feat(feed): accent-insensitive search (unaccent)

Feed text search used plain ILIKE, which is case- but not diacritic-insensitive, so 'tiesto'
missed the many titles spelled 'Tiësto' — a search that ingested ~45 results showed only ~12.
Enable the postgres unaccent extension (migration 0029) and wrap both sides of the title/
channel match in unaccent(), so 'tiesto' now matches 'Tiësto'. Applies to feed, count and
facets alike.

backend/alembic/versions/0029_unaccent_search.py

@@ -0,0 +1,31 @@
+"""accent-insensitive feed search (unaccent)
+
+Revision ID: 0029_unaccent_search
+Revises: 0028_live_search_provenance
+Create Date: 2026-06-29
+
+Enables the PostgreSQL `unaccent` contrib extension so the feed's text search can match
+regardless of diacritics — e.g. searching "tiesto" finds titles spelled "Tiësto". The feed
+query wraps both sides in unaccent(); this migration just makes the function available.
+`unaccent` ships with the official postgres image (postgresql-contrib). The DB role is a
+superuser in our deployments, so CREATE EXTENSION succeeds; IF NOT EXISTS keeps it idempotent.
+"""
+from typing import Sequence, Union
+
+from alembic import op
+
+revision: str = "0029_unaccent_search"
+down_revision: Union[str, None] = "0028_live_search_provenance"
+branch_labels: Union[str, Sequence[str], None] = None
+depends_on: Union[str, Sequence[str], None] = None
+
+
+def upgrade() -> None:
+    op.execute("CREATE EXTENSION IF NOT EXISTS unaccent")
+
+
+def downgrade() -> None:
+    # Intentionally left in place: other code/queries may rely on unaccent() and dropping a
+    # contrib extension is rarely what's wanted on a downgrade. (The feed query reverts with
+    # the code, not this migration.)
+    pass

backend/app/routes/feed.py

@@ -205,8 +205,15 @@ def _filtered_query(
         ) + timedelta(days=1)
         query = query.where(Video.published_at < end)
     if q:
-        like = f"%{q}%"
+        # Accent-insensitive: unaccent() both sides so "tiesto" matches "Tiësto" (ILIKE alone
-        query = query.where(or_(Video.title.ilike(like), Channel.title.ilike(like)))
+        # is case- but not diacritic-insensitive). unaccent is enabled by migration 0029.
+        like = func.unaccent(f"%{q}%")
+        query = query.where(
+            or_(
+                func.unaccent(Video.title).ilike(like),
+                func.unaccent(Channel.title).ilike(like),
+            )
+        )
 
     if tags:
         # AND across tag categories (e.g. language AND topic narrows), OR within a