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/lib/hooks.ts

@@ -9,8 +9,9 @@ import { fileAuthHeaders, fileDownloadUrl } from '@/lib/api/upload';
  * into a blob URL rather than a direct URL. `ref` is anything fileDownloadUrl accepts: a full
  * "/v0/file/s/xxx" path (Drafty `refurl`), or an absolute URL.
  */
-export function useAuthedBlobUrl(ref: string | undefined): { url: string | null; loading: boolean; error: boolean } {
+export function useAuthedBlobUrl(ref: string | undefined): { url: string | null; loading: boolean; error: boolean; retry: () => void } {
   const [state, setState] = useState<{ url: string | null; loading: boolean; error: boolean }>({ url: null, loading: !!ref, error: false });
+  const [retryCount, setRetryCount] = useState(0);
 
   useEffect(() => {
     if (!ref) return undefined;
@@ -34,9 +35,9 @@ export function useAuthedBlobUrl(ref: string | undefined): { url: string | null;
       cancelled = true;
       if (objectUrl) URL.revokeObjectURL(objectUrl);
     };
-  }, [ref]);
+  }, [ref, retryCount]);
 
-  return state;
+  return { ...state, retry: () => setRetryCount((n) => n + 1) };
 }
 
 /** Ported from the old app's use-cached-data.js -- debounces a fast-changing value (e.g. search input). */