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/models.py

@@ -199,6 +199,12 @@ class Thread(Base):
     has_attachments: Mapped[bool] = mapped_column(nullable=False, server_default=text("false"))
     pinned: Mapped[bool] = mapped_column(nullable=False, server_default=text("false"))
     last_message_at: Mapped[dt.datetime] = mapped_column(TIMESTAMP(timezone=True), nullable=False)
+    # Snooze: out of the Inbox until this time (NULL when not snoozed). A message
+    # that arrives after ``snoozed_at`` wakes it early; ``unsnoozed_at`` (when it
+    # last woke) puts it back at the top of the Inbox.
+    snoozed_until: Mapped[dt.datetime | None] = mapped_column(TIMESTAMP(timezone=True))
+    snoozed_at: Mapped[dt.datetime | None] = mapped_column(TIMESTAMP(timezone=True))
+    unsnoozed_at: Mapped[dt.datetime | None] = mapped_column(TIMESTAMP(timezone=True))
 
 
 class Message(Base):
@@ -263,6 +269,17 @@ class Message(Base):
     snippet: Mapped[str] = mapped_column(Text, nullable=False, server_default=text("''"))
     blob_sha256: Mapped[str] = mapped_column(Text, nullable=False)
     body_indexed: Mapped[str | None] = mapped_column(TSVECTOR)
+    # Mailing-list headers, for the Subscriptions page. ``list_unsubscribe`` is
+    # NULL until read (a backfill job fills older mail), '' when there is none.
+    list_id: Mapped[str | None] = mapped_column(Text)
+    list_unsubscribe: Mapped[str | None] = mapped_column(Text)
+    # RFC 8058: the sender takes a one-click unsubscribe POST.
+    list_unsubscribe_post: Mapped[bool] = mapped_column(
+        nullable=False, server_default=text("false")
+    )
+    # The language of its text (app/translation.py), found the first time it is
+    # shown: NULL not looked at yet, '' could not tell.
+    content_language: Mapped[str | None] = mapped_column(Text)
 
 
 class BodyPart(Base):
@@ -276,6 +293,8 @@ class BodyPart(Base):
     content: Mapped[str] = mapped_column(Text, nullable=False)
     # SPEC §10.4: re-sanitize on render if the sanitizer version changed.
     sanitizer_v: Mapped[int] = mapped_column(Integer, nullable=False, server_default=text("0"))
+    # Tracking pixels taken out of this HTML (shown as "N trackers blocked").
+    trackers_blocked: Mapped[int] = mapped_column(Integer, nullable=False, server_default=text("0"))
 
 
 class Attachment(Base):
@@ -404,6 +423,78 @@ class Invitation(Base):
     )
 
 
+class SubscriptionState(Base):
+    """What a user did about a bulk sender on the Subscriptions page."""
+
+    __tablename__ = "subscription_states"
+
+    user_id: Mapped[uuid.UUID] = mapped_column(
+        UUID(as_uuid=True), ForeignKey("users.id", ondelete="CASCADE"), primary_key=True
+    )
+    # The sender group: "list:<List-Id>" or "from:<address>".
+    key: Mapped[str] = mapped_column(Text, primary_key=True)
+    unsubscribed_at: Mapped[dt.datetime] = _now()
+    method: Mapped[str] = mapped_column(Text, nullable=False)  # one_click | mailto | web
+
+
+class MailTemplate(Base):
+    """A saved reply, inserted from the compose window."""
+
+    __tablename__ = "mail_templates"
+
+    id: Mapped[uuid.UUID] = _uuid_pk()
+    user_id: Mapped[uuid.UUID] = mapped_column(
+        UUID(as_uuid=True), ForeignKey("users.id", ondelete="CASCADE"), nullable=False, index=True
+    )
+    name: Mapped[str] = mapped_column(Text, nullable=False)
+    subject: Mapped[str] = mapped_column(Text, nullable=False, server_default=text("''"))
+    body_html: Mapped[str] = mapped_column(Text, nullable=False, server_default=text("''"))
+    created_at: Mapped[dt.datetime] = _now()
+    updated_at: Mapped[dt.datetime] = _now()
+
+
+class MessageTranslation(Base):
+    """A message's HTML translated into a language (app/translation.py), kept so
+    it is translated once. ``images``: with remote images shown or not."""
+
+    __tablename__ = "message_translations"
+
+    message_id: Mapped[uuid.UUID] = mapped_column(
+        UUID(as_uuid=True), ForeignKey("messages.id", ondelete="CASCADE"), primary_key=True
+    )
+    target: Mapped[str] = mapped_column(Text, primary_key=True)
+    images: Mapped[bool] = mapped_column(primary_key=True)
+    source: Mapped[str] = mapped_column(Text, nullable=False)
+    html: Mapped[str] = mapped_column(Text, nullable=False)
+    sanitizer_v: Mapped[int] = mapped_column(Integer, nullable=False)
+    created_at: Mapped[dt.datetime] = _now()
+
+
+class CompletionPhrase(Base):
+    """Sentence completion (app/completion.py): after these words, the user
+    usually writes this — seen ``count`` times in their sent mail."""
+
+    __tablename__ = "completion_phrases"
+
+    user_id: Mapped[uuid.UUID] = mapped_column(
+        UUID(as_uuid=True), ForeignKey("users.id", ondelete="CASCADE"), primary_key=True
+    )
+    context: Mapped[str] = mapped_column(Text, primary_key=True)  # normalized words
+    continuation: Mapped[str] = mapped_column(Text, primary_key=True)  # as written
+    count: Mapped[int] = mapped_column(Integer, nullable=False)
+
+
+class CompletionIndexState(Base):
+    """When a user's completion index was last built."""
+
+    __tablename__ = "completion_index_state"
+
+    user_id: Mapped[uuid.UUID] = mapped_column(
+        UUID(as_uuid=True), ForeignKey("users.id", ondelete="CASCADE"), primary_key=True
+    )
+    built_at: Mapped[dt.datetime] = mapped_column(TIMESTAMP(timezone=True), nullable=False)
+
+
 class PushSubscription(Base):
     """A browser or installed app to tell about new mail (Web Push)."""