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/auth/RegisterPage.tsx

@@ -1,4 +1,4 @@
-import { useState } from 'react';
+import { useEffect, useState } from 'react';
 
 import { Link, Navigate, useNavigate } from 'react-router-dom';
 
@@ -41,6 +41,14 @@ export function RegisterPage() {
   const [formError, setFormError] = useState('');
   const [submitting, setSubmitting] = useState(false);
 
+  // A challengeId/code pair is only valid for the phone number it was issued for -- without this,
+  // editing the phone after requesting a code (typo fix) leaves a stale challengeId in place that
+  // verifyRegisterCode() has no way to cross-check against the NEW phone in the field.
+  useEffect(() => {
+    setChallengeId('');
+    setCode('');
+  }, [phone]);
+
   if (!tenant) return <Navigate to="/tenant" replace />;
 
   const usingPhone = !!phone;