Merge the typing game into the music player as a tab, with lock/unlock UI

Moves tippen from a standalone app into web/ as a third tab (audio player /
smarthome / typing), replacing the old single room-toggle corner button with a
vertical icon tab rail. Curriculum and progress now come from the backend
(musicmouse/tippen/*) instead of a build-time YAML import and localStorage.

Adds reward-driven lock rendering: Cover/BrowseView/AlbumModal show a question
mark for locked albums/tracks with a hint on what unlocks them, and
ResultSheet gets a new unlock-animation block alongside the existing
lesson-unlock and aquarium-creature celebrations.

CSS from the two apps is merged carefully: identical rules (bubble/card/
key-cap/view-enter/backdrop-enter and their keyframes) are shared as-is,
while rules that bake in each app's own hue are kept separate under a
`tp-` prefix and scoped to the typing tab's own .tp-stage wrapper, so
neither app's look bleeds into the other's.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

web/src/lib/keyboard.ts

@@ -25,8 +25,8 @@ export interface UiState {
    * that row", the way it means "which flat position" everywhere else. */
   shelfRow: number;
   /** Which top-level page is showing. Orthogonal to `view`/`search`/`group`/… below,
-   * so toggling to the room and back leaves the music side exactly as it was. */
-  page: "music" | "room";
+   * so switching pages and back leaves the music side exactly as it was. */
+  page: "music" | "room" | "typing";
   view: "browse" | "play";
   openAlbumId: string | null;
   /** Which track is highlighted in the open album's track list. Only meaningful while
@@ -232,6 +232,12 @@ export function handleKey(
 ): Action[] {
   const { key } = event;
 
+  // The typing tab is a second app mounted alongside this one (TippenApp.tsx) with its
+  // own complete keyboard handling, including its own Escape/F1 bindings. It must own
+  // every key while active - even Shift+media and Space below, which would otherwise
+  // hijack a key a lesson happens to be drilling (see TippenApp.tsx's own doc comment).
+  if (state.page === "typing") return [];
+
   if (event.shiftKey && !event.ctrlKey && !event.metaKey) {
     const media = SHIFT_MEDIA[key.toUpperCase()];
     if (media) return media;