fix(e8): deep-review hardening + cut 0.73.0

Fixes from several multi-agent deep-review passes over the E8 feed-filtering &
channel-manager epic (S1-S4):
- feed_years buckets by UTC year to match the UTC-pinned year-filter bounds
- tag suggestions: examples ∩ subscribed (drop tagged-then-unsubscribed channels
  from the profile denominator); exclude hidden channels as suggestion targets
- channel manager: restore ghost chips + surface an error toast on a failed tag accept
- year filter: debounce the search term so the per-year facet doesn't refetch per keystroke
- channel tags: aria-label the "+N" overflow pills
- extract useTagSuggestions hook; add backend + hook tests (profile boundaries, cap,
  language exclusion, unsubscribed/hidden handling, UTC bucketing, bulk-accept)

Bump VERSION to 0.73.0 + release notes.

frontend/src/lib/releaseNotes.ts

@@ -14,6 +14,21 @@ export interface ReleaseEntry {
 }
 
 export const RELEASE_NOTES: ReleaseEntry[] = [
+  {
+    version: "0.73.0",
+    date: "2026-08-26",
+    summary:
+      "Feed filtering and the Channel Manager catch up with Plex: filter to channels you haven't tagged, filter the feed by year, hover any card for its full details, and let Siftlode suggest your own tags for untagged channels based on how you've tagged similar ones.",
+    features: [
+      "New “No tag” filter — narrow the feed and the Channel Manager to channels you haven't personally tagged yet, so what still needs organising is easy to find.",
+      "Filter the feed by year: quick chips for recent years with per-year video counts, plus a “More…” dialog listing every year, sortable by year or count.",
+      "Hover (or keyboard-focus) any feed card for an info box with the full title, channel, date, duration, a description snippet, and the channel's tags — without opening the video.",
+      "The Channel Manager now suggests your own tags for untagged channels, learned from how you've tagged similar ones. Accept a suggestion with one tap, dismiss it, or accept all the confident ones at once.",
+    ],
+    chores: [
+      "The whole epic went through several multi-agent deep-review passes — findings fixed and re-reviewed each round until it came back clean.",
+    ],
+  },
   {
     version: "0.72.1",
     date: "2026-08-24",