Feat: festes Avatar-VRM (das eine Modell) + Avatar-Picker entfernt

Avatar fest auf /avatar.vrm (frontend/public/avatar.vrm → dist). Galerie/Upload/URL raus;
AvatarPicker → reine VoiceControls (nur Stimme). vrmStore.ts gelöscht. avatar.vrm ist gitignored
(23 MB, lizenz-/redistributionssensibel) — liegt auf der Box, nicht in git.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

frontend/src/lib/voice/vrmStore.ts

@@ -1,35 +0,0 @@
-// Winziger IndexedDB-Wrapper, um ein hochgeladenes .vrm (ArrayBuffer) über Reloads hinweg zu
-// behalten. localStorage scheidet aus (VRMs sind oft 5–40 MB). Ein einziger Record genügt.
-
-const DB = "mc2-voice"
-const STORE = "avatar"
-const KEY = "uploaded-vrm"
-
-function open(): Promise<IDBDatabase> {
-  return new Promise((resolve, reject) => {
-    const req = indexedDB.open(DB, 1)
-    req.onupgradeneeded = () => req.result.createObjectStore(STORE)
-    req.onsuccess = () => resolve(req.result)
-    req.onerror = () => reject(req.error)
-  })
-}
-
-export async function saveUploadedVrm(buf: ArrayBuffer): Promise<void> {
-  const db = await open()
-  await new Promise<void>((resolve, reject) => {
-    const tx = db.transaction(STORE, "readwrite")
-    tx.objectStore(STORE).put(buf, KEY)
-    tx.oncomplete = () => resolve()
-    tx.onerror = () => reject(tx.error)
-  })
-}
-
-export async function loadUploadedVrm(): Promise<ArrayBuffer | null> {
-  const db = await open()
-  return new Promise((resolve, reject) => {
-    const tx = db.transaction(STORE, "readonly")
-    const req = tx.objectStore(STORE).get(KEY)
-    req.onsuccess = () => resolve((req.result as ArrayBuffer) ?? null)
-    req.onerror = () => reject(req.error)
-  })
-}