fix(downloads): add the downloads package (was wrongly gitignored) + robust sanitizer

The .gitignore 'downloads/' pattern for the DOWNLOAD_ROOT bind mount also matched the
backend/app/downloads source package, so formats.py/storage.py/service.py never got
committed with M2. Anchor the ignore to '/downloads/' (repo root only) and add the package.

storage.sanitize() now handles arbitrarily messy titles (emoji, ZWJ, fullwidth, clickbait
punctuation): NFKC-normalize, drop emoji/symbol/control unicode categories, collapse
repeated punctuation, underscore-join words -> space-free paths. Accents (HU/DE) preserved,
no ASCII folding. Plex layout uses _-_ separators + Season_{year}.

backend/app/downloads/storage.py

@@ -0,0 +1,143 @@
+"""On-disk layout for downloaded media — Plex-friendly tree + .nfo/poster sidecars.
+
+The physical filename is system-decided and bound to the source id (never renamed; the user's
+custom name is display-only, applied at local-download time). Layout is admin-configurable:
+
+  plex:  {Channel}/Season {Year}/{Channel} - {YYYY-MM-DD} - {title} [{id}].{ext}
+  flat:  {title} [{id}].{ext}
+
+Plus a Kodi/Plex-readable `<basename>.nfo` (episodedetails) and `<basename>.jpg` thumbnail, so
+a Plex library using a metadata agent picks up rich info. Channel = "show", video = episode,
+date-based — the community-standard mapping for YouTube-in-Plex.
+"""
+import re
+import shutil
+import unicodedata
+from dataclasses import dataclass
+from datetime import date
+from pathlib import Path
+from xml.sax.saxutils import escape
+
+# Reserve room for the " [id].ext" suffix + parent dirs within the 255-byte component limit.
+_MAX_TITLE = 120
+# Filesystem-illegal on Windows/Plex + control chars.
+_ILLEGAL = re.compile(r'[<>:"/\\|?*\x00-\x1f]')
+# Unicode categories we drop entirely: emoji/pictographs (So), modifier symbols/skin-tones
+# (Sk), and every control/format/private/surrogate/unassigned char (C*). Letters (incl.
+# accented á/ö/ü/ß), digits, and ordinary punctuation are KEPT — Siftlode is trilingual, so
+# ASCII-folding would mangle Hungarian/German titles.
+_DROP_CATEGORIES = {"So", "Sk", "Cc", "Cf", "Cs", "Co", "Cn"}
+
+
+@dataclass
+class MediaMeta:
+    video_id: str
+    title: str
+    uploader: str
+    upload_date: date | None
+    duration_s: int | None = None
+    description: str | None = None
+    thumbnail_url: str | None = None
+
+
+def sanitize(name: str, limit: int = _MAX_TITLE) -> str:
+    """Turn an arbitrary (emoji-laden, clickbait) title into a clean, space-free path token.
+
+    Steps: NFKC-normalize (fold fancy width/compat forms) → drop emoji/symbols/control chars →
+    strip filesystem-illegal chars → collapse whitespace and runs of the same punctuation →
+    join words with underscores → trim junk punctuation from the ends → length-cap. Accented
+    letters and digits survive; the result never contains spaces or path separators."""
+    text = unicodedata.normalize("NFKC", name or "")
+    text = "".join(
+        ch for ch in text if unicodedata.category(ch) not in _DROP_CATEGORIES
+    )
+    text = _ILLEGAL.sub("", text)
+    # Collapse repeated punctuation ("!!!", "???", "-----") to a single mark.
+    text = re.sub(r"([^\w\s])\1{1,}", r"\1", text)
+    # Whitespace → single underscore (no spaces in generated names).
+    text = re.sub(r"\s+", "_", text.strip())
+    # Tidy separator pile-ups and trim junk from the ends.
+    text = re.sub(r"_{2,}", "_", text).strip("_.-·—–|,;:!?ّ ")
+    if len(text) > limit:
+        text = text[:limit].rstrip("_.-")
+    return text or "untitled"
+
+
+def rel_path(meta: MediaMeta, ext: str, layout: str = "plex") -> str:
+    """Path of the media file relative to DOWNLOAD_ROOT (forward slashes)."""
+    title = sanitize(meta.title)
+    vid = meta.video_id
+    if layout == "flat":
+        return f"{title}_[{vid}].{ext}"
+    channel = sanitize(meta.uploader or "Unknown_Channel", 80)
+    year = meta.upload_date.year if meta.upload_date else 0
+    d = meta.upload_date.isoformat() if meta.upload_date else "0000-00-00"
+    epname = f"{channel}_-_{d}_-_{title}_[{vid}].{ext}"
+    return f"{channel}/Season_{year}/{epname}"
+
+
+def abs_path(download_root: str, rel: str) -> Path:
+    return Path(download_root) / rel
+
+
+def place_file(staging_file: Path, download_root: str, rel: str) -> None:
+    """Move a completed staging file into its final location under DOWNLOAD_ROOT."""
+    dest = abs_path(download_root, rel)
+    dest.parent.mkdir(parents=True, exist_ok=True)
+    shutil.move(str(staging_file), str(dest))
+
+
+def _nfo_xml(meta: MediaMeta) -> str:
+    aired = meta.upload_date.isoformat() if meta.upload_date else ""
+    year = meta.upload_date.year if meta.upload_date else ""
+    parts = [
+        '<?xml version="1.0" encoding="UTF-8" standalone="yes"?>',
+        "<episodedetails>",
+        f"  <title>{escape(meta.title or '')}</title>",
+        f"  <showtitle>{escape(meta.uploader or '')}</showtitle>",
+        f"  <studio>{escape(meta.uploader or '')}</studio>",
+        f"  <aired>{aired}</aired>",
+        f"  <premiered>{aired}</premiered>",
+        f"  <year>{year}</year>",
+        f"  <plot>{escape(meta.description or '')}</plot>",
+        f"  <uniqueid type=\"youtube\" default=\"true\">{escape(meta.video_id)}</uniqueid>",
+    ]
+    if meta.duration_s:
+        parts.append(f"  <runtime>{round(meta.duration_s / 60)}</runtime>")
+    parts.append("</episodedetails>")
+    return "\n".join(parts)
+
+
+def write_sidecars(
+    download_root: str, rel: str, meta: MediaMeta, thumb_src: Path | None
+) -> bool:
+    """Write `<basename>.nfo` + `<basename>.jpg` next to the media file. Returns True if written."""
+    media = abs_path(download_root, rel)
+    base = media.with_suffix("")
+    try:
+        base.with_suffix(".nfo").write_text(_nfo_xml(meta), encoding="utf-8")
+        if thumb_src and thumb_src.exists():
+            shutil.copyfile(str(thumb_src), str(base.with_suffix(".jpg")))
+        return True
+    except OSError:
+        return False
+
+
+def delete_asset_files(download_root: str, rel: str) -> None:
+    """Remove the media file and its sidecars; prune now-empty parent dirs (best effort)."""
+    media = abs_path(download_root, rel)
+    base = media.with_suffix("")
+    for p in (media, base.with_suffix(".nfo"), base.with_suffix(".jpg")):
+        try:
+            p.unlink()
+        except OSError:
+            pass
+    # Prune empty Season/Channel dirs up to (but not including) the root.
+    root = Path(download_root).resolve()
+    parent = media.parent
+    while parent != root and root in parent.parents:
+        try:
+            parent.rmdir()  # only succeeds if empty
+        except OSError:
+            break
+        parent = parent.parent