feat(m5a): channel manager, tabbed settings panel, per-user sync status

Backend: /api/channels (list + PATCH priority/hidden + attach/detach user tags),
user-tag CRUD on /api/tags, /api/sync/my-status (per-user channel sync counts).
Frontend: feed|channels page nav (URL-synced) from the account menu; a slide-in
tabbed Settings panel (Appearance, Notifications=6b sound+duration, Sync status +
actions + admin pause/resume, Account); a channel manager with priority, hide,
per-channel user tags, sync badges and 'view in feed'. Notifications now honor the
configurable sound + auto-dismiss settings.

backend/app/main.py

@@ -26,7 +26,7 @@ from starlette.middleware.sessions import SessionMiddleware
 
 from app import auth
 from app.config import settings
-from app.routes import feed, health, me, sync, tags
+from app.routes import channels, feed, health, me, sync, tags
 from app.scheduler import shutdown_scheduler, start_scheduler
 
 
@@ -65,6 +65,7 @@ app.include_router(sync.router)
 app.include_router(tags.router)
 app.include_router(feed.router)
 app.include_router(me.router)
+app.include_router(channels.router)
 
 # The built SPA (populated by the Docker frontend build stage).
 STATIC_DIR = Path(__file__).parent / "static_spa"

backend/app/routes/channels.py

@@ -0,0 +1,143 @@
+"""Channel manager: the user's subscriptions with their personal overrides (priority,
+hidden, tags) and per-channel sync state. Read + local-write only — YouTube-side writes
+(unsubscribe) live behind the optional write scope and are added in a later phase."""
+from fastapi import APIRouter, Depends, HTTPException
+from sqlalchemy import and_, func, select
+from sqlalchemy.orm import Session
+
+from app.auth import current_user
+from app.db import get_db
+from app.models import Channel, ChannelTag, Subscription, Tag, User, Video
+
+router = APIRouter(prefix="/api/channels", tags=["channels"])
+
+
+@router.get("")
+def list_channels(
+    user: User = Depends(current_user), db: Session = Depends(get_db)
+) -> list[dict]:
+    rows = db.execute(
+        select(Subscription, Channel)
+        .join(Channel, Channel.id == Subscription.channel_id)
+        .where(Subscription.user_id == user.id)
+        .order_by(Subscription.priority.desc(), func.lower(Channel.title))
+    ).all()
+
+    # Per-channel stored video count (shared data) in one grouped query.
+    channel_ids = [c.id for _, c in rows]
+    stored: dict[str, int] = {}
+    if channel_ids:
+        for cid, count in db.execute(
+            select(Video.channel_id, func.count(Video.id))
+            .where(Video.channel_id.in_(channel_ids))
+            .group_by(Video.channel_id)
+        ).all():
+            stored[cid] = count
+
+    # The user's personal tag links, grouped by channel.
+    tags_by_channel: dict[str, list[int]] = {}
+    for cid, tag_id in db.execute(
+        select(ChannelTag.channel_id, ChannelTag.tag_id).where(
+            ChannelTag.user_id == user.id
+        )
+    ).all():
+        tags_by_channel.setdefault(cid, []).append(tag_id)
+
+    return [
+        {
+            "id": ch.id,
+            "title": ch.title,
+            "handle": ch.handle,
+            "thumbnail_url": ch.thumbnail_url,
+            "subscriber_count": ch.subscriber_count,
+            "video_count": ch.video_count,
+            "stored_videos": stored.get(ch.id, 0),
+            "priority": sub.priority,
+            "hidden": sub.hidden,
+            "tag_ids": tags_by_channel.get(ch.id, []),
+            "details_synced": ch.details_synced_at is not None,
+            "recent_synced": ch.recent_synced_at is not None,
+            "backfill_done": ch.backfill_done,
+        }
+        for sub, ch in rows
+    ]
+
+
+def _user_subscription(db: Session, user: User, channel_id: str) -> Subscription:
+    sub = db.execute(
+        select(Subscription).where(
+            Subscription.user_id == user.id, Subscription.channel_id == channel_id
+        )
+    ).scalar_one_or_none()
+    if sub is None:
+        raise HTTPException(status_code=404, detail="Not subscribed to this channel")
+    return sub
+
+
+@router.patch("/{channel_id}")
+def update_channel(
+    channel_id: str,
+    payload: dict,
+    user: User = Depends(current_user),
+    db: Session = Depends(get_db),
+) -> dict:
+    sub = _user_subscription(db, user, channel_id)
+    if "priority" in payload:
+        sub.priority = int(payload["priority"])
+    if "hidden" in payload:
+        sub.hidden = bool(payload["hidden"])
+    db.commit()
+    return {"id": channel_id, "priority": sub.priority, "hidden": sub.hidden}
+
+
+@router.post("/{channel_id}/tags")
+def attach_tag(
+    channel_id: str,
+    payload: dict,
+    user: User = Depends(current_user),
+    db: Session = Depends(get_db),
+) -> dict:
+    _user_subscription(db, user, channel_id)
+    tag_id = payload.get("tag_id")
+    tag = db.get(Tag, tag_id) if tag_id is not None else None
+    # Only the user's own tags may be attached as personal links.
+    if tag is None or tag.user_id != user.id:
+        raise HTTPException(status_code=404, detail="Unknown tag")
+    exists = db.execute(
+        select(ChannelTag).where(
+            ChannelTag.channel_id == channel_id,
+            ChannelTag.tag_id == tag_id,
+            ChannelTag.user_id == user.id,
+        )
+    ).scalar_one_or_none()
+    if exists is None:
+        db.add(
+            ChannelTag(
+                channel_id=channel_id,
+                tag_id=tag_id,
+                user_id=user.id,
+                source="user",
+            )
+        )
+        db.commit()
+    return {"channel_id": channel_id, "tag_id": tag_id}
+
+
+@router.delete("/{channel_id}/tags/{tag_id}")
+def detach_tag(
+    channel_id: str,
+    tag_id: int,
+    user: User = Depends(current_user),
+    db: Session = Depends(get_db),
+) -> dict:
+    row = db.execute(
+        select(ChannelTag).where(
+            ChannelTag.channel_id == channel_id,
+            ChannelTag.tag_id == tag_id,
+            ChannelTag.user_id == user.id,
+        )
+    ).scalar_one_or_none()
+    if row is not None:
+        db.delete(row)
+        db.commit()
+    return {"channel_id": channel_id, "tag_id": tag_id}

backend/app/routes/sync.py

@@ -1,5 +1,5 @@
 from fastapi import APIRouter, Depends, HTTPException
-from sqlalchemy import func, select
+from sqlalchemy import and_, case, func, select
 from sqlalchemy.orm import Session
 
 from app import quota, state
@@ -93,6 +93,50 @@ def sync_status(
     }
 
 
+@router.get("/my-status")
+def my_status(
+    user: User = Depends(current_user), db: Session = Depends(get_db)
+) -> dict:
+    """Per-user sync progress: how far the channels *this* user subscribes to have synced."""
+    sub_join = and_(
+        Subscription.channel_id == Channel.id, Subscription.user_id == user.id
+    )
+    total, details_synced, recent_synced, deep_done = db.execute(
+        select(
+            func.count(Channel.id),
+            func.count(Channel.details_synced_at),
+            func.count(Channel.recent_synced_at),
+            func.sum(case((Channel.backfill_done.is_(True), 1), else_=0)),
+        )
+        .select_from(Channel)
+        .join(Subscription, sub_join)
+    ).one()
+    total = total or 0
+    deep_done = int(deep_done or 0)
+    my_videos = db.scalar(
+        select(func.count(Video.id)).join(
+            Subscription,
+            and_(
+                Subscription.channel_id == Video.channel_id,
+                Subscription.user_id == user.id,
+                Subscription.hidden.is_(False),
+            ),
+        )
+    )
+    return {
+        "channels_total": total,
+        "channels_details_synced": details_synced,
+        "channels_recent_synced": recent_synced,
+        "channels_deep_done": deep_done,
+        "channels_recent_pending": total - recent_synced,
+        "channels_deep_pending": total - deep_done,
+        "my_videos": my_videos or 0,
+        "quota_used_today": quota.units_used_today(db),
+        "quota_remaining_today": quota.remaining_today(db),
+        "paused": state.is_sync_paused(db),
+    }
+
+
 @router.post("/pause")
 def pause_sync(
     user: User = Depends(current_user), db: Session = Depends(get_db)

backend/app/routes/tags.py

@@ -32,6 +32,66 @@ def list_tags(user: User = Depends(current_user), db: Session = Depends(get_db))
     ]
 
 
+@router.post("")
+def create_tag(
+    payload: dict,
+    user: User = Depends(current_user),
+    db: Session = Depends(get_db),
+) -> dict:
+    name = (payload.get("name") or "").strip()
+    if not name:
+        raise HTTPException(status_code=400, detail="name is required")
+    category = payload.get("category") or "other"
+    tag = Tag(
+        user_id=user.id,
+        name=name,
+        color=payload.get("color"),
+        category=category if category in ("language", "topic", "other") else "other",
+    )
+    db.add(tag)
+    db.commit()
+    return {"id": tag.id, "name": tag.name, "color": tag.color, "category": tag.category}
+
+
+def _own_tag(db: Session, user: User, tag_id: int) -> Tag:
+    tag = db.get(Tag, tag_id)
+    if tag is None or tag.user_id != user.id:
+        # System tags (user_id NULL) are not user-editable.
+        raise HTTPException(status_code=404, detail="Unknown tag")
+    return tag
+
+
+@router.patch("/{tag_id}")
+def update_tag(
+    tag_id: int,
+    payload: dict,
+    user: User = Depends(current_user),
+    db: Session = Depends(get_db),
+) -> dict:
+    tag = _own_tag(db, user, tag_id)
+    if "name" in payload:
+        name = (payload.get("name") or "").strip()
+        if not name:
+            raise HTTPException(status_code=400, detail="name cannot be empty")
+        tag.name = name
+    if "color" in payload:
+        tag.color = payload.get("color")
+    db.commit()
+    return {"id": tag.id, "name": tag.name, "color": tag.color, "category": tag.category}
+
+
+@router.delete("/{tag_id}")
+def delete_tag(
+    tag_id: int,
+    user: User = Depends(current_user),
+    db: Session = Depends(get_db),
+) -> dict:
+    tag = _own_tag(db, user, tag_id)
+    db.delete(tag)  # ChannelTag rows cascade on tag delete.
+    db.commit()
+    return {"deleted": tag_id}
+
+
 @router.post("/recompute")
 def recompute(
     user: User = Depends(current_user),