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/api/mailboxes.py

@@ -12,7 +12,7 @@ from sqlalchemy.ext.asyncio import AsyncSession
 
 from app.db import get_session
 from app.identity.deps import CurrentUser
-from app.models import Draft, Mailbox, Message
+from app.models import Draft, Mailbox, Message, Thread
 from app.outbox.service import not_being_sent
 
 router = APIRouter(prefix="/mailboxes", tags=["mail"])
@@ -30,6 +30,7 @@ class MailboxOut(BaseModel):
 class FolderCounts(BaseModel):
     inbox_unread: int  # unread messages sitting in Inbox mailboxes
     drafts: int  # drafts shown in the Drafts folder (local + un-adopted remote)
+    snoozed: int = 0  # conversations snoozed out of the Inbox
 
 
 @router.get("", response_model=list[MailboxOut])
@@ -54,8 +55,17 @@ async def folder_counts(user: CurrentUser, db: DbSession) -> FolderCounts:
             Message.user_id == user.id,
             Mailbox.special_use == "inbox",
             ~Message.flags.contains(["\\Seen"]),
+            # A snoozed conversation is out of the Inbox until it wakes.
+            ~Message.thread_id.in_(
+                select(Thread.id).where(Thread.user_id == user.id, Thread.snoozed_until.isnot(None))
+            ),
         )
     )
+    snoozed = await db.scalar(
+        select(func.count())
+        .select_from(Thread)
+        .where(Thread.user_id == user.id, Thread.snoozed_until.isnot(None))
+    )
 
     # Drafts folder = local drafts + IMAP-Drafts messages we haven't adopted (mirror
     # UIDs excluded), matching what list_drafts + list_remote_drafts return.
@@ -77,4 +87,8 @@ async def folder_counts(user: CurrentUser, db: DbSession) -> FolderCounts:
     )
     remote = sum(1 for r in remote_rows if (r.account_id, r.uid) not in owned)
 
-    return FolderCounts(inbox_unread=int(inbox_unread or 0), drafts=int(local or 0) + remote)
+    return FolderCounts(
+        inbox_unread=int(inbox_unread or 0),
+        drafts=int(local or 0) + remote,
+        snoozed=int(snoozed or 0),
+    )