fix(web): code review round 2 -- messaging UI bugs and design fidelity

- DetailColumn: remark-edit draft and the history-search modal's open
  state weren't reset on contact switch (no key={topicId}, same long-
  lived instance) -- could silently save a typed remark against the
  WRONG contact. History-search state lifted to MessagesLayout so
  ConversationView's header search icon (previously wired to nothing)
  can open the same modal
- ConversationView: loadOlder's in-flight "restore scroll position"
  callback and its loading flag weren't guarded against a conversation
  switch happening mid-request, and the scroll-to-bottom effect keyed
  only on messages.length so two conversations that happened to load
  the same page size never got scrolled down on open
- ChatListColumn: pinned 系统消息/文件助手 rows used solid-color-square
  avatars like regular contacts; the actual design-code source
  (ChatList.dc.html) and reference screenshots use a light tinted
  background with a colored icon instead
- MessageBubble: own ("我") messages hash-colored their avatar like any
  contact instead of the design's fixed accent blue
- Every send/recall/favorite/forward action swallowed its own failure
  silently (empty .catch or, for forward, no catch at all) -- moved
  Toast from features/auth into app/ (shared) and wired real error
  feedback through it
- MessageContextMenu: added the recall countdown label, Escape-to-close,
  and viewport-edge clamping (a right-click near the window edge could
  render partially off-screen)
- EmojiPanel now defaults to 最近 per the reference (was defaulting to
  表情)
- HistorySearchModal: pagination (searchTopicMessages/getTopicMedia both
  supported cursor/next_cursor already, nothing used it -- silently
  truncated at one page), Escape-to-close, and a brief "没有找到" flash
  on the first keystroke before the debounce caught up
- A handful of design-token corrections (--shadow-btn, NavRail's border/
  spacing, LoginPage's logo radius/brand-panel padding, a placeholder
  icon color) verified against screens/*.dc.html's exact pixel values

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

web/src/features/auth/EnterpriseRegisterPage.tsx

@@ -1,9 +1,9 @@
 import { useState } from 'react';
 
-import { Link } from 'react-router-dom';
+import { Link, useLocation } from 'react-router-dom';
 
 import { Icon } from '@/app/Icon';
-import { Toast } from '@/features/auth/components/Toast';
+import { Toast } from '@/app/Toast';
 import { ImApiError } from '@/lib/api/client';
 import { submitTenantApplication, uploadPublicFile } from '@/lib/api/tenant';
 
@@ -12,6 +12,7 @@ const EMAIL_RE = /^[^\s@]+@[^\s@]+\.[^\s@]+$/;
 
 /** README §10.5 / old app's EnterpriseRegister -- a company registering itself as a new tenant. */
 export function EnterpriseRegisterPage() {
+  const tenantCodeHint = (useLocation().state as { tenantCodeHint?: string } | null)?.tenantCodeHint || undefined;
   const [creditCode, setCreditCode] = useState('');
   const [email, setEmail] = useState('');
   const [file, setFile] = useState<File | null>(null);
@@ -32,7 +33,12 @@ export function EnterpriseRegisterPage() {
       if (file) {
         licenseFileId = (await uploadPublicFile(file, 'enterprise_license')).file_id;
       }
-      const data = await submitTenantApplication({ credit_code: creditCode, enterprise_email: email || undefined, license_file_id: licenseFileId });
+      const data = await submitTenantApplication({
+        credit_code: creditCode,
+        enterprise_email: email || undefined,
+        license_file_id: licenseFileId,
+        tenant_code_hint: tenantCodeHint,
+      });
       setReviewDays(Math.max(1, Math.round((data.estimated_review_hours || 24) / 24)));
       setSubmitted(true);
       setToast('提交成功，我们会尽快联系你');