refactor: hook dependencies name everything the hooks read

The 12 react-hooks/exhaustive-deps warnings the gate let through:
- ShareDialog and YearFilter built a fresh [] per render while their query loaded, so their
  memos recomputed on every render; they share one empty list now.
- VideoEditor's drag effect called a seek/moveBoundary recreated each render; both are stable
  callbacks in its deps.
- WizardProvider re-checks onboarding on exactly the fields it reads (not the me object, whose
  60 s refetch would reopen a closed wizard).
- Channels, Feed and PlexPlayer list the stable values they already used.
- The player's keydown effect is bound once on purpose (its helpers read refs): said so, with a
  disable, as the codebase's other deliberate sites do.
- dialogFocus and the YouTube player's cleanup read refs React may already have let go of; they
  use what they captured when the effect ran.

frontend/src/components/Channels.tsx

@@ -292,7 +292,7 @@ export default function Channels() {
     if (filtersResetToken === resetRef.current) return;
     resetRef.current = filtersResetToken;
     setSearch("");
-  }, [filtersResetToken]);
+  }, [filtersResetToken, setSearch]);
 
   // Tag/priority/text filters stay controlled COLUMN filters (`filters.tags` etc.) shared by the top
   // chips, the column funnels and the cards. The sync-status filter (`filters.sync`) is no longer a