Add /dashboard route, mark-all-watched on complete, keyboard fixes

- Move dashboard page to app/(pages)/dashboard, redirect / to /dashboard
  for authenticated users, update all nav/breadcrumb/auth hrefs
- Mark all episodes watched when a TV show status is set to "completed"
  (markAllEpisodesWatched skips already-watched episodes)
- Refactor KeyboardProvider to store shortcuts in a ref instead of
  state, eliminating unnecessary re-renders; use react-hotkeys-hook for
  Cmd+K so it works reliably in form inputs
- Fix useRegisterShortcut: re-register on every render (stable ref read)
  with a separate cleanup effect, removing brittle key memoization
- Search page: silently navigate to title detail on import instead of
  showing "Added to library" toast

components/keyboard-help-dialog.tsx

@@ -10,11 +10,11 @@ import {
 import { Kbd } from "@/components/ui/kbd";
 
 export function KeyboardHelpDialog() {
-  const { shortcuts, helpOpen, setHelpOpen } = useKeyboard();
+  const { shortcutsRef, helpOpen, setHelpOpen } = useKeyboard();
 
   // Group shortcuts by scope
   const grouped: Record<string, { description: string; keys: string[] }[]> = {};
-  for (const def of shortcuts.values()) {
+  for (const def of shortcutsRef.current.values()) {
     const scope = def.scope ?? "Global";
     if (!grouped[scope]) grouped[scope] = [];
     grouped[scope].push({ description: def.description, keys: def.keys });