feat(feed): per-category any/all tag match, in each combobox's popover footer

The tag 'Match: Any/All' toggle was a single GLOBAL setting that only ever
affected topics, shown as its own row under the Topic widget. Make it
per-category — language, topic, and 'your tags' each get their own independent
any/all — and move it into each filter combobox's popover footer (like
SortControl's direction segment), reclaiming the standalone Match row.

Backend: the feed query already groups selected tags by category; replace the
single tag_mode with per-category tag_mode_language/topic/other params and apply
the conjunctive (HAVING all) branch per category. Mirrored across filtered_query,
feed_summary.passes(), and the /facets drill-down exclusion (kept in lockstep;
equivalence test updated to tag_mode_topic). No schema change.

Frontend: FeedFilters.tagMode -> tagModes {language,topic,other} (pure leaf
lib/api/tagModes with a coerceTagModes migration for the legacy global value);
serialized to the API and the shareable URL per category (legacy ?tagmode=and
still resolves into the topic slot); saved-view blobs migrate on read. Combobox
gains an optional matchMode/onMatchModeChange footer segment, shown once 2+
values are picked; the three tag comboboxes wire it to their category.

Verified: backend feed tests green (12, incl. the count/facets equivalence net);
live, the footer appears at 2+ selections, toggles aria-pressed, serializes
tagmode_topic=and to the URL, and the request carries tag_mode_topic=and (200).
374 vitest, tsc, ruff, eslint (0 err).

backend/app/feedquery.py

@@ -117,7 +117,7 @@ def filtered_query(
     user: User,
     *,
     tags: list[int],
-    tag_mode: str,
+    tag_modes: dict[str, str],
     channel_ids: list[str],
     q: str | None,
     min_duration: int | None,
@@ -293,9 +293,10 @@ def filtered_query(
             query = query.where(or_(func.unaccent(Video.title).ilike(like), channel_match))
 
     if tags:
-        # AND across tag categories (e.g. language AND topic narrows), OR within a category; the any/all
-        # toggle controls multiple topic tags. ⚠️ feed_summary.passes() reimplements this exact rule in
-        # Python for the sidebar count/facets — keep the two in lockstep (equivalence-tested by
+        # AND across tag categories (e.g. language AND topic narrows), OR within a category — unless that
+        # category's mode is "and" (its per-category any/all toggle), which requires a channel to carry
+        # ALL its selected tags. ⚠️ feed_summary.passes() reimplements this exact rule in Python for the
+        # sidebar count/facets — keep the two in lockstep (equivalence-tested by
         # test_feed_summary_matches_count_plus_facets).
         by_category = tags_by_category(db, tags)
         # Facet counting drops the category being counted so its own chips don't zero each
@@ -305,7 +306,7 @@ def filtered_query(
             by_category.pop(exclude_tag_category, None)
         visible = or_(ChannelTag.user_id.is_(None), ChannelTag.user_id == user.id)
         for category, ids in by_category.items():
-            if category == "topic" and tag_mode == "and" and len(ids) > 1:
+            if tag_modes.get(category, "or") == "and" and len(ids) > 1:
                 sub = (
                     select(ChannelTag.channel_id)
                     .where(ChannelTag.tag_id.in_(ids), visible)
@@ -363,8 +364,8 @@ def feed_summary(db: Session, user: User, **params) -> dict:
                  (the tag's own category dropped, unless it's a conjunctive topic-AND — mirroring the
                  old /facets exclude_tag_category logic exactly).
     Tag matching is channel-based, identical to filtered_query's tag block (AND across categories, OR
-    within, topic-AND requires ALL selected topics)."""
-    tag_mode = params.get("tag_mode", "or")
+    within, a category in "and" mode requires ALL its selected tags)."""
+    tag_modes = params.get("tag_modes", {})
 
     # ONE pass: per-channel video counts for the base filter, tags stripped so every candidate channel
     # is present to facet over.
@@ -401,8 +402,8 @@ def feed_summary(db: Session, user: User, **params) -> dict:
         for cat, sel in selected_by_cat.items():
             if cat == exclude_cat:
                 continue
-            if cat == "topic" and tag_mode == "and" and len(sel) > 1:
-                if not sel <= ch_tags:  # conjunctive: channel must carry ALL selected topics
+            if tag_modes.get(cat, "or") == "and" and len(sel) > 1:
+                if not sel <= ch_tags:  # conjunctive: channel must carry ALL this category's selected tags
                     return False
             elif not (sel & ch_tags):  # disjunctive: channel must carry ANY selected tag
                 return False
@@ -416,7 +417,7 @@ def feed_summary(db: Session, user: User, **params) -> dict:
     for category in ("language", "topic", "other"):
         # Drop this category's own selections so its chips keep independent counts; a conjunctive
         # topic-AND keeps them (each remaining chip narrows to channels that ALSO have the selected).
-        exclude = None if (category == "topic" and tag_mode == "and") else category
+        exclude = None if tag_modes.get(category, "or") == "and" else category
         for cid, ch_tags in channel_tags.items():
             if not passes(ch_tags, exclude):
                 continue