feat(channels): search box + clickable tag chips; fix(feed): contextual Your-tags

- Channels manager: prominent channel-name search box and the 'Your tags' chips are now
  clickable to filter the table by tag (replacing the hidden per-column DataTable popovers).
  Both filter client-side over the status-filtered list; a focus-channel intent seeds the
  search, the reset intent clears both.
- Feed 'Your tags' sidebar: count user tags in the facet endpoint (the 'other' category) and
  make the widget contextual like language/topic — counts reflect the current filter and
  zero-count chips hide (e.g. a source=search view with no tagged channels shows 'no matching
  tags' instead of the full static list). EN/HU/DE searchPlaceholder.

frontend/src/components/Sidebar.tsx

@@ -182,7 +182,8 @@ export default function Sidebar({
   const languages = tags.filter((t) => t.category === "language");
   const topics = tags.filter((t) => t.category === "topic");
   // The user's own (non-system) tags — those assigned to channels in the Channel manager.
-  // Facets only cover language/topic, so these show their static channel_count.
+  // Facets cover them too now (the "other" category), so they're contextual like the rest:
+  // zero-count chips hide once facets load, counts reflect the current filter.
   const userTags = tags.filter((t) => !t.system);
   const [customDates, setCustomDates] = useState(false);
   const [tagManagerOpen, setTagManagerOpen] = useState(false);
@@ -407,18 +408,22 @@ export default function Sidebar({
           </>
         );
       }
-      case "tags":
+      case "tags": {
+        const tagChips = visibleChips(userTags);
         return (
           <div className="flex flex-wrap items-center gap-1.5">
-            {userTags.map((tg) => (
+            {tagChips.map((tg) => (
               <TagChip
                 key={tg.id}
                 tag={tg}
-                count={tg.channel_count}
+                count={chipCount(tg)}
                 active={filters.tags.includes(tg.id)}
                 onClick={() => toggleTag(tg.id)}
               />
             ))}
+            {facetsReady && tagChips.length === 0 && (
+              <span className="text-[11px] text-muted">{t("sidebar.noMatchingTags")}</span>
+            )}
             <button
               onClick={() => setTagManagerOpen(true)}
               title={t("sidebar.manageTags")}
@@ -429,6 +434,7 @@ export default function Sidebar({
             </button>
           </div>
         );
+      }
     }
   }