Sender avatars, PDF password preview, contacts autosave, account-view + Trash/Spam auto-purge, UI polish

Sender avatars (privacy-safe, server-fetched, cached):
- New GET /api/avatar resolves Gravatar (d=404) then the sender domain's favicon
  under the SSRF guard, Redis-cached (hit+miss); gated by SENDER_AVATARS_ENABLED.
  GuardedResponse gains raw bytes. Shown in the mail list, reading pane, People
  panel, and Contacts (overlay that falls back to initials on a miss).

PDF preview:
- Password-protected PDFs now prompt in-place and retry (pdf.js PasswordException),
  with a clear error for other load failures instead of a blank overlay. The
  password is remembered per attachment until the thread is left; clicking the
  field no longer dismisses the overlay.

Contacts:
- Autosave reply recipients: message.sent now carries to/cc (name+email); the
  contacts plugin subscribes and adds any non-contact recipients to the Autosaved
  group. Contact avatars show the gravatar/favicon via /api/avatar.

Mail views / retention:
- Clicking an account shows all its mail except Trash/Spam (was inbox-only).
- Daily cron autopurge_trash_spam permanently deletes Trash/Spam older than
  TRASH_RETENTION_DAYS (default 30; 0 disables) — server EXPUNGE + local rows.

UI polish:
- Ultimo signet logo in the Mail/Calendar/Contacts sidebar header and collapsed
  rail; consistent 11px top margin and vertically-aligned header row across states
  (fixed-size flex icon buttons); SVG favicon on the browser tab.

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

frontend/src/components/thread/ThreadView.tsx

@@ -9,6 +9,8 @@ import type { AccountOut, MailboxOut, MessageEnvelope } from "../../lib/types";
 import { PluginSlot } from "../../plugins/PluginSlot";
 import { Composer, type ComposerInit } from "../compose/Composer";
 import { Icon } from "../Icon";
+import { AvatarImage } from "../SenderAvatar";
+import { clearPdfPasswordCache } from "./AttachmentPreview";
 import { LabelChips } from "../mail/LabelChips";
 import { MessageBody } from "./MessageBody";
 
@@ -345,10 +347,11 @@ function MessageItem({
   const nameColor = accentColor ?? `hsl(${h} 55% 62%)`;
   const avatar = () => (
     <span
-      className="flex h-10 w-10 shrink-0 items-center justify-center rounded-full text-sm font-semibold text-white"
+      className="relative flex h-10 w-10 shrink-0 items-center justify-center overflow-hidden rounded-full text-sm font-semibold text-white"
       style={{ backgroundColor: avatarBg }}
     >
       {initials(message)}
+      <AvatarImage email={message.from_addr[0]?.email} />
     </span>
   );
   const senderName = (
@@ -534,6 +537,8 @@ export function ThreadView({
   // --- labels: per-message storage + a thread union for display (chips + list) ---
   const messageIds = useMemo(() => messages.map((m) => m.id), [messages]);
   const threadId = messages[0]?.thread_id ?? null;
+  // Forget remembered protected-PDF passwords when the open thread changes or closes.
+  useEffect(() => () => clearPdfPasswordCache(), [threadId]);
   const allLabelsQuery = useQuery({ queryKey: ["labels-all"], queryFn: api.labelsAll });
   const msgLabelsQuery = useQuery({
     queryKey: ["message-labels", messageIds],