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>

docker/docker-compose.yml

@@ -158,6 +158,24 @@ services:
       retries: 12
     restart: unless-stopped
 
+  # Email translation (app/translation.py). The first start downloads every
+  # language model (several GB) into the volume; later starts reuse them.
+  libretranslate:
+    image: libretranslate/libretranslate:v1.9.6
+    environment:
+      LT_DISABLE_WEB_UI: "true"
+      LT_UPDATE_MODELS: "false"
+    ports:
+      - "127.0.0.1:5005:5000"
+    volumes:
+      - ltmodels:/home/libretranslate/.local
+    healthcheck:
+      test: ["CMD-SHELL", "python3 -c \"import urllib.request; urllib.request.urlopen('http://127.0.0.1:5000/languages', timeout=4)\""]
+      interval: 15s
+      timeout: 6s
+      retries: 240
+    restart: unless-stopped
+
   greenmail:
     image: greenmail/standalone:2.0.1
     environment:
@@ -170,6 +188,7 @@ services:
       - "127.0.0.1:3993:3993"   # IMAPS
 
 volumes:
+  ltmodels:
   pgdata:
   meilidata:
   blobs: