Replace idb with idb-keyval for draft media storage

Simplifies web IndexedDB storage by using idb-keyval instead of the
full idb library. This reduces bundle size and aligns with the pattern
used in src/storage/archive/db/index.web.ts.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

package.json

@@ -172,7 +172,6 @@
     "history": "^5.3.0",
     "hls.js": "^1.6.2",
     "idb-keyval": "^6.2.2",
-    "idb": "^8.0.3",
     "js-sha256": "^0.9.0",
     "jwt-decode": "^4.0.0",
     "lande": "^1.0.10",