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

frontend/icons/hide.svg

@@ -0,0 +1 @@
+<svg xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" aria-hidden="true" role="img" width="64" height="64" viewBox="0 0 24 24" style="color: rgb(74, 85, 101); opacity: 1; transform: rotate(0deg);"><path fill="none" stroke="currentColor" stroke-linecap="round" stroke-linejoin="round" stroke-width="2" d="m4 4l16 16m-3.5-3.244C15.147 17.485 13.618 18 12 18c-3.53 0-6.634-2.452-8.413-4.221c-.47-.467-.705-.7-.854-1.159c-.107-.327-.107-.913 0-1.24c.15-.459.385-.693.855-1.16c.897-.892 2.13-1.956 3.584-2.793M19.5 14.634c.333-.293.638-.582.912-.854l.003-.003c.468-.466.703-.7.852-1.156c.107-.327.107-.914 0-1.241c-.15-.458-.384-.692-.854-1.159C18.633 8.452 15.531 6 12 6q-.507 0-1 .064m2.323 7.436a2 2 0 0 1-2.762-2.889"></path></svg>

frontend/icons/show.svg

@@ -0,0 +1 @@
+<svg xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" aria-hidden="true" role="img" width="64" height="64" viewBox="0 0 24 24" style="color: rgb(74, 85, 101); opacity: 1; transform: rotate(0deg);"><g fill="none" stroke="currentColor" stroke-linecap="round" stroke-linejoin="round" stroke-width="2"><path d="M3.587 13.779c1.78 1.769 4.883 4.22 8.413 4.22s6.634-2.451 8.413-4.22c.47-.467.705-.7.854-1.159c.107-.327.107-.913 0-1.24c-.15-.458-.385-.692-.854-1.159C18.633 8.452 15.531 6 12 6c-3.53 0-6.634 2.452-8.413 4.221c-.47.467-.705.7-.854 1.159c-.107.327-.107.913 0 1.24c.15.458.384.692.854 1.159"></path><path d="M10 12a2 2 0 1 0 4 0a2 2 0 0 0-4 0"></path></g></svg>