Translation on Firefox Translations models; new logo

- Email translation moves from LibreTranslate to our own translator
  service (translator/): Mozilla's Firefox Translations models on the
  Bergamot engine, fastText language detection (176 languages). Polish,
  English, German, French, Spanish and Italian on first start (~350 MB
  instead of ~10 GB); Admin panel > Email translation installs and
  removes languages. Built and pushed as the `translator` image.
- Every message is translated paragraph by paragraph as plain text;
  names travel with their sentence and are kept only where the model
  changed them; a sentence start the model copied ("Enclosed") is tried
  again in lower case; list markers are not sent
- The Translate button shows only for installed languages
- New logo: favicon, app/maskable/iPhone icons, notification badge,
  email logo and calendar copy regenerated; BIMI logo rebuilt in SVG
  Tiny PS with its gradients; masks render in browsers
- Launch screen background is the app's dark grey

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

backend/app/api/admin.py

@@ -15,10 +15,12 @@ import re
 import uuid
 from typing import Annotated
 
-from fastapi import APIRouter, Depends, Query
+from fastapi import APIRouter, Depends, Path, Query
+from pydantic import BaseModel
 from sqlalchemy import func, select
 from sqlalchemy.ext.asyncio import AsyncSession
 
+from app import translation
 from app.api.errors import raise_api_error
 from app.config import get_settings
 from app.db import get_session
@@ -332,3 +334,61 @@ async def remove_user(user_id: uuid.UUID, admin: CurrentAdmin, db: DbSession) ->
     except MailServerError as exc:
         raise_api_error(502, "mail_server_unavailable", f"the mail server did not answer: {exc}")
     return {"status": "deleted"}
+
+
+# --- email translation languages (translator service) ------------------------------
+
+
+class InstallProgressOut(BaseModel):
+    done: int
+    total: int
+
+
+class AdminTranslationOut(BaseModel):
+    enabled: bool  # TRANSLATOR_URL is set
+    reachable: bool
+    installed: list[str] = []
+    installing: dict[str, InstallProgressOut] = {}
+    available: list[str] = []  # what Mozilla has models for (empty: offline)
+    errors: dict[str, str] = {}  # why a language's last install failed
+
+
+_LANG = Path(pattern=r"^[a-z]{2,3}(-[A-Za-z]{2,4})?$")
+
+
+@router.get("/translation", response_model=AdminTranslationOut)
+async def translation_status(admin: CurrentAdmin) -> AdminTranslationOut:
+    if not translation.enabled():
+        return AdminTranslationOut(enabled=False, reachable=False)
+    try:
+        data = await translation.status()
+    except translation.TranslationError:
+        return AdminTranslationOut(enabled=True, reachable=False)
+    return AdminTranslationOut(enabled=True, reachable=True, **data)
+
+
+@router.post(
+    "/translation/languages/{code}",
+    response_model=AdminTranslationOut,
+    dependencies=[Depends(require_csrf)],
+)
+async def install_language(admin: CurrentAdmin, code: str = _LANG) -> AdminTranslationOut:
+    """Download a language's models (to and from English) in the background."""
+    try:
+        await translation.install(code)
+    except translation.TranslationError as exc:
+        raise_api_error(502, "translator_failed", str(exc))
+    return await translation_status(admin)
+
+
+@router.delete(
+    "/translation/languages/{code}",
+    response_model=AdminTranslationOut,
+    dependencies=[Depends(require_csrf)],
+)
+async def remove_language(admin: CurrentAdmin, code: str = _LANG) -> AdminTranslationOut:
+    try:
+        await translation.remove(code)
+    except translation.TranslationError as exc:
+        raise_api_error(502, "translator_failed", str(exc))
+    return await translation_status(admin)