fix(web): code review round 3 -- UI bugs and remaining design fidelity

- FileAttachment never surfaced a failed authenticated download -- the
  card looked identically clickable whether it worked or not, and
  clicking while broken silently no-op'd. Added an error state/retry
  (useAuthedBlobUrl gained a retry() escape hatch for this).
  ImageAttachment/AudioAttachment already handled this; only the file
  card didn't.
- --shadow-btn was one token serving two different specs: round 2's fix
  (0 6px 16px, from the 50px auth CTAs) actually regressed the 36px
  messaging send button (ConversationView/VoiceRecorder), which needs
  0 4px 12px per 02-messages.dc.html. Split into --shadow-btn /
  --shadow-btn-sm.
- loadOlder's scroll-restore guard compared topicId by value, which
  false-positives on an A->B->A round trip within one request's
  lifetime (same string, but the DOM was torn down and rebuilt by the
  intervening open/close). Switched to a generation counter, same
  pattern as topics.ts's leave-race fix.
- errorToast wasn't included in ConversationView/DetailColumn's
  topicId-reset effects -- a failed action's toast could keep showing
  over a conversation/contact switched to afterward. Also switched
  those effects (and MessagesLayout's) from useEffect to
  useLayoutEffect -- since none of these components remount on
  topicId change, a post-paint effect could let one frame render with
  the previous topicId's stale UI still showing.
- VoiceRecorder never listened for MediaRecorder's own onerror -- a
  mid-recording failure left the "录音中" timer ticking forever with no
  indication the recording had already died.
- VerificationCodeButton's phone-change countdown reset (round 2) only
  cleared the button's own state; RegisterPage/ResetPasswordPage's
  challengeId was still tied to whatever phone the code was actually
  issued for, with nothing cross-checking it against a since-edited
  phone number.
- Agreement's checkbox used bare accent-color on a native input, which
  only tints the checked fill and leaves size/radius/border to the
  browser/OS; replaced with the spec's exact 16x16 border-radius:4px
  box + check glyph.
- Added a catch-all route (App.tsx), TenantFeedbackPage image-picker
  validation feedback + corrected remove-button style, and a handful of
  smaller token/spacing corrections against screens/*.dc.html (NavRail
  font-weight, LoginPage/TenantEntryPage logo size+shadow+color,
  ChatListColumn row padding/icon size, --shadow-modal alpha).

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

web/src/features/messages/ChatListColumn.tsx

@@ -73,10 +73,10 @@ export function ChatListColumn() {
             <Link
               key={entry.key}
               to={entry.route}
-              className="grid min-h-[68px] grid-cols-[44px_minmax(0,1fr)_auto] items-center gap-3 border-b border-list-item bg-white px-4 py-2.5 no-underline hover:bg-[#f6f8fb]"
+              className="grid min-h-[68px] grid-cols-[44px_minmax(0,1fr)_auto] items-center gap-3 border-b border-list-item bg-white py-2.5 pl-4 pr-3 no-underline hover:bg-[#f6f8fb]"
             >
               <span className={`grid h-11 w-11 place-items-center rounded-lg ${entry.colorClass}`}>
-                <Icon name={entry.icon} className="text-[22px]" />
+                <Icon name={entry.icon} className="text-2xl" />
               </span>
               <span className="flex min-w-0 flex-col gap-1">
                 <strong className="truncate text-[15px] font-medium text-[#272b31]">{entry.label}</strong>
@@ -105,7 +105,7 @@ export function ChatListColumn() {
               <Link
                 key={contact.topic}
                 to={`/messages/${contact.topic}`}
-                className={`grid min-h-[68px] grid-cols-[44px_minmax(0,1fr)_auto] items-center gap-3 border-b border-list-item px-4 py-2.5 no-underline ${
+                className={`grid min-h-[68px] grid-cols-[44px_minmax(0,1fr)_auto] items-center gap-3 border-b border-list-item py-2.5 pl-4 pr-3 no-underline ${
                   active ? 'bg-accent-selected-bg' : 'bg-white hover:bg-[#f6f8fb]'
                 }`}
               >