mail UX: restore-to-folder, draft/attachment fixes, printing, sidebar collapse

Backend:
- Restore returns each message to its original folder (e.g. Sent/Archive) instead
  of always the Inbox: new messages.restore_mailbox_id (migration 0010) +
  restore_thread_job.
- Drafts: expunge reconciliation for the Drafts poll (provider.list_uids /
  _reconcile_drafts) clears phantom "remote" drafts; send + discard drop the
  mirrored DB row; adopting a remote draft carries its real attachments into the
  compose flow.
- Thread detail/list are folder-aware: individually trashed/spam messages are
  hidden outside their folder, Trash/Spam show only their own messages, and the
  mail-list message count matches the view.

Frontend:
- Thread reading panel: fix newest-first card overlap/spacing (expand-all and
  single expand), hide Reply/Forward on trashed messages, close the Actions menu
  on message-body (iframe) clicks, scroll to the inline composer, and prompt
  Save draft / Discard on the X close.
- Composer: remount when switching drafts, dirty-tracking to stop duplicate IMAP
  mirrors, and close the From/More dropdowns on outside click.
- Sidebar: collapse/expand toggle (icons-only ~60px rail) and a log-out icon on
  Sign out.
- Mail-standard printing in a new window with reliable page margins (lib/print.ts).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01U72FZiF1W1pb8XxyWBTREA

backend/tests/api/test_api.py

@@ -254,6 +254,50 @@ async def test_thread_detail_messages_ascending(api: ApiCtx) -> None:
     assert dates == sorted(dates)  # ascending
 
 
+async def test_thread_detail_hides_trashed_message_unless_viewing_trash(api: ApiCtx) -> None:
+    assert api.session is not None
+    # Give the account a Trash folder and delete a single message of the 2-message
+    # kickoff thread (move it to Trash) — as the per-message Delete action does.
+    trash = Mailbox(
+        account_id=api.account_id, user_id=api.user_id, path="Trash", special_use="trash"
+    )
+    api.session.add(trash)
+    await api.session.flush()
+    resp = await api.client.get("/api/threads")
+    kickoff = next(t for t in resp.json()["threads"] if t["message_count"] == 2)
+    detail = (await api.client.get(f"/api/threads/{kickoff['id']}")).json()
+    victim = uuid.UUID(detail["messages"][-1]["id"])
+    msg = await api.session.get(Message, victim)
+    assert msg is not None
+    msg.mailbox_id = trash.id
+    await api.session.commit()
+
+    # Viewing the thread from the Inbox: the trashed message is gone.
+    inbox_view = await api.client.get(
+        f"/api/threads/{kickoff['id']}", params={"view": "folder:inbox"}
+    )
+    ids = [m["id"] for m in inbox_view.json()["messages"]]
+    assert str(victim) not in ids
+    assert len(ids) == 1
+
+    # Viewing from the Trash folder: only the trashed message is shown (Trash is
+    # message-scoped), not the rest of the conversation.
+    trash_view = await api.client.get(
+        f"/api/threads/{kickoff['id']}", params={"view": "folder:trash"}
+    )
+    ids_trash = [m["id"] for m in trash_view.json()["messages"]]
+    assert ids_trash == [str(victim)]
+
+    # The Inbox LIST count drops the trashed message (was 2, now 1); the Trash list
+    # counts only the one trashed message.
+    inbox_list = await api.client.get("/api/threads", params={"view": "folder:inbox"})
+    row = next(t for t in inbox_list.json()["threads"] if t["id"] == kickoff["id"])
+    assert row["message_count"] == 1
+    trash_list = await api.client.get("/api/threads", params={"view": "folder:trash"})
+    trow = next(t for t in trash_list.json()["threads"] if t["id"] == kickoff["id"])
+    assert trow["message_count"] == 1
+
+
 async def test_message_html_is_sanitized(api: ApiCtx) -> None:
     # the lunch message has HTML with a script
     resp = await api.client.get("/api/threads")