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-compose.yml

@@ -71,6 +71,8 @@ x-backend-env: &backend-env
   RSPAMD_CONTROLLER_PASSWORD: ${RSPAMD_CONTROLLER_PASSWORD}
   # Spelling and grammar check in the compose window. Empty turns it off.
   LANGUAGETOOL_URL: ${LANGUAGETOOL_URL-http://languagetool:8010}
+  # Email translation; empty turns it off.
+  LIBRETRANSLATE_URL: ${LIBRETRANSLATE_URL-http://libretranslate:5000}
   LOG_LEVEL: ${LOG_LEVEL:-INFO}
   UNDO_SECONDS: ${UNDO_SECONDS:-10}
   SESSION_TTL_DAYS: ${SESSION_TTL_DAYS:-30}
@@ -109,12 +111,13 @@ services:
       - |
         set -e
         mkdir -p /mnt/postgres /mnt/blobs /mnt/backups /mnt/redis /mnt/meili /mnt/state \
-          /mnt/languagetool-ngrams
+          /mnt/languagetool-ngrams /mnt/libretranslate
         # Only recurse when ownership is actually wrong: `chown -R` over a large
         # blob store on every start would be minutes of pointless disk churn.
         [ "$$(stat -c %u /mnt/blobs)" = "10001" ] || chown -R 10001:10001 /mnt/blobs
         [ "$$(stat -c %u /mnt/backups)" = "999" ] || chown -R 999:999 /mnt/backups
         [ "$$(stat -c %u /mnt/redis)" = "999" ]   || chown -R 999:999 /mnt/redis
+        [ "$$(stat -c %u /mnt/libretranslate)" = "1032" ] || chown -R 1032:65534 /mnt/libretranslate
         chmod 700 /mnt/backups
         echo "[init] data directories ready"
     volumes:
@@ -313,6 +316,32 @@ services:
     cpus: ${LANGUAGETOOL_CPUS:-1.0}
     logging: *logging
 
+  # Email translation (app/translation.py), all on this server. The first
+  # start downloads every language model (a few GB) into DATA_ROOT; later
+  # starts reuse them. A model is loaded into memory the first time its
+  # language is used.
+  libretranslate:
+    image: libretranslate/libretranslate:v1.9.6
+    environment:
+      LT_DISABLE_WEB_UI: "true"
+      LT_UPDATE_MODELS: "false"
+      LT_THREADS: ${LIBRETRANSLATE_THREADS:-2}
+      TZ: ${TZ:-UTC}
+    volumes:
+      - ${DATA_ROOT:-/NO-.env-FOUND-RUN-deploy_webmail.sh-init-FIRST}/libretranslate:/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: 30s
+      timeout: 6s
+      retries: 5
+      start_period: 30m  # the first start downloads the models
+    depends_on:
+      init: { condition: service_completed_successfully }
+    restart: unless-stopped
+    mem_limit: ${LIBRETRANSLATE_MEM_LIMIT:-6g}
+    cpus: ${LIBRETRANSLATE_CPUS:-2.0}
+    logging: *logging
+
   # Bayes tokens and fuzzy hashes. Separate from the app's redis on purpose
   # (§C.2): this data is derived and retrainable, so it trades durability for
   # room to grow — RDB snapshots every 5 min, and an eviction policy, where the