refactor(js): extract attachments, autofill, unlock modules from app.js (3.1)

app.js 9363 -> 7962 lines. Three new classic-script modules:
- app.attachments.js (250): blob crypto + upload/download UI, pure
  declarations, loads before app.js
- app.autofill.js (276): Win32 combos, title->entry matching, picker,
  pure declarations, loads before app.js
- app.unlock.js (907): Quick Unlock + PIN + recovery code grouped (same
  "enter without master pw" theme); assigns Bridge.onPinResult /
  onQuickUnlockResult at top level so it loads AFTER app.js, like app.sync.js

Audit viewer stays in app.js (only 65 lines, not worth a file). Clipboard
bridge helpers stay too (were interleaved in the quick-unlock section but
unrelated). Registered in BuildAssets whitelist + index.html + APP_PARTS.
Verified in-app: quick unlock cold-start, attachment upload/download.

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

index.html

@@ -1228,7 +1228,10 @@
 <script src="js/app.backup.js"></script>
 <script src="js/app.health.js"></script>
 <script src="js/app.overlays.js"></script>
+<script src="js/app.attachments.js"></script>
+<script src="js/app.autofill.js"></script>
 <script src="js/app.js"></script>
+<script src="js/app.unlock.js"></script>
 <script src="js/app.sync.js"></script>
 </body>
 </html>