Two-way draft sync, signatures, sent/bcc fixes, and mail-list UI

Backend
- Sent copies: persist locally on send + periodic multi-folder CONDSTORE poll
  (Sent/Archive/Trash/Junk) so they thread and show without an IDLE-only INBOX.
- Bcc: transmitted copy omits Bcc, Sent copy keeps it; store/display bcc_addr.
- Drafts: mirror local drafts to the IMAP Drafts folder (append/replace/expunge);
  inbound sync of foreign drafts (un-threaded) with adopt-to-edit + dedup by UID.
- Per-user storage quota (5 GiB default) and manual "sync all folders" action.
- Account editing (display/color/server/password) and per-account HTML signature.
- Account view scoped to that account's inbox; new migrations 0006–0009.

Frontend
- Mail-list pagination, folder filters (All/Unread/Pinned), sort toggle, refresh.
- Aligned + widened mail-list margins; reading-pane bars fixed height.
- Rich-text composer: color palette, highlight, image; attachments; expand/pop-out.
- Signatures: auto-insert for new mail, replace on From change, reply insert.
- Restore/Delete actions per folder; drafts view merges local + remote, date-sorted.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

frontend/src/components/list/MessageList.tsx

@@ -61,18 +61,13 @@ export function MessageList({
                 height: item.size,
                 transform: `translateY(${item.start}px)`,
               }}
-              className={`flex flex-col gap-1 border-b border-app-border px-3 py-2.5 text-left ${
+              className={`flex flex-col gap-1 border-b border-app-border px-6 py-2.5 text-left ${
                 selected
                   ? "bg-app-active"
                   : "hover:bg-app-hover"
               }`}
             >
               <div className="flex items-center gap-2">
-                {unread ? (
-                  <span className="h-2 w-2 shrink-0 rounded-full bg-app-accent" />
-                ) : (
-                  <span className="h-2 w-2 shrink-0" />
-                )}
                 <span className="flex shrink-0 gap-0.5">
                   {thread.account_ids.map((id) => (
                     <span
@@ -95,11 +90,11 @@ export function MessageList({
                 )}
                 <span className="shrink-0 text-[11px] text-app-faint">{timeLabel(thread.last_message_at)}</span>
               </div>
-              <div className={`truncate pl-4 text-[13px] ${unread ? "font-medium text-app-fg" : "text-app-muted"}`}>
+              <div className={`truncate text-[13px] ${unread ? "font-medium text-app-fg" : "text-app-muted"}`}>
                 {thread.subject}
                 {thread.has_attachments && <span className="ml-1 text-app-faint">📎</span>}
               </div>
-              <div className="truncate pl-4 text-xs text-app-faint">{thread.snippet}</div>
+              <div className="truncate text-xs text-app-faint">{thread.snippet}</div>
             </button>
           );
         })}