Productivity features, UI translations, local email translation

- Snooze (with a Snoozed folder), keyboard shortcuts with a Settings
  section, mail templates (Compose > More > Templates), a Subscriptions
  folder with bulk unsubscribe/delete, and tracker blocking with a
  Privacy toggle (on by default)
- Own dialogs instead of browser popups; emoji picker in compose; compose
  windows survive a visit to Settings
- Sentence completion learned from the user's sent mail (no AI)
- Interface in English and Polish (one file per language, English as the
  fallback), picked from the browser on first run, then kept
- Email translation on the server via LibreTranslate: Translate button
  and "Translate to...", messages in several languages translated part
  by part, names/addresses/emoji/file names/phone numbers kept, an
  animated line while translating
- Antispam "Mark as spam" loads with the message, not when the menu opens

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

backend/app/indexer/indexer.py

@@ -25,6 +25,7 @@ from app.indexer.sanitize import sanitize_html
 from app.models import Account, Attachment, BodyPart, KnownRecipient, Message
 from app.providers.base import RemoteMessage
 from app.search.base import SearchDoc
+from app.subscriptions import read_list_headers
 from app.threading_.normalize import synthesize_message_id
 from app.threading_.threader import thread_message
 
@@ -167,6 +168,7 @@ async def persist_message(
     else:
         sha = rawstore.put_cached(user_id, remote.raw)
     parsed = await _parse_bounded(user_id, sha, remote.raw)
+    list_headers = read_list_headers(remote.raw)  # for the Subscriptions page
 
     message_id_hdr = await _resolve_message_id(
         session, user_id=user_id, account_id=account_id, parsed_id=parsed.message_id, raw=remote.raw
@@ -207,6 +209,9 @@ async def persist_message(
         has_attachments=parsed.has_attachments,
         snippet=parsed.snippet,
         blob_sha256=sha,
+        list_id=list_headers.list_id,
+        list_unsubscribe=list_headers.unsubscribe,
+        list_unsubscribe_post=list_headers.one_click,
     )
     session.add(message)
     await session.flush()
@@ -224,6 +229,7 @@ async def persist_message(
                 kind="html_sanitized",
                 content=result.html,
                 sanitizer_v=result.sanitizer_v,
+                trackers_blocked=result.trackers_blocked,
             )
         )