fix(web): code review round 1 -- critical data-layer bugs

Three parallel adversarial code-review passes surfaced real defects across
the app. This commit covers the data/logic layer:

- CRITICAL: file upload/download used the wrong auth header entirely.
  Built from docs/IM-前后端对接文档.md as `X-MeetingIM-Auth: token <token>`,
  but the old app's own upload code carries an explicit comment that the
  real header is `Authorization: Token <token>` (capitalized scheme,
  standard header name), "verified live against the real server, not just
  read from source" -- and separately warns the SDK's own built-in
  LargeFileHelper gets this wrong too (sends X-Tinode-APIKey/X-Tinode-Auth,
  which this backend doesn't recognize). This means every external
  (non-inline) image/file/voice attachment -- anything too large to send as
  base64 -- was silently broken; only the earlier live tests happened to
  use small inline attachments, which never exercise this code path.
  Confirmed fixed live: a real >256KB image now uploads (200, real file_id)
  and downloads (blob URL, correct 800x600 dimensions) correctly.
- CRITICAL: TopicMe.onContactUpdate was never wired. Marking a conversation
  read (topic.noteRead()) updates the contact's unread count through ONLY
  this single-slot callback (confirmed against the SDK's own
  Topic.note()/TopicMe._refreshContact -- it does not also fire onData/
  onInfo/onPres, unlike every other _refreshContact call site, which do).
  Without it the chat list's unread badge/ordering went stale after reading
  a conversation until an unrelated topic event happened to invalidate the
  shared snapshot cache.
- HIGH: chat-list message preview didn't check isServerDeleted(msg) (the
  `hi` soft-delete flag), only `content == null` -- a hi-flagged message
  with non-null content leaked its real text/attachment label into the
  preview instead of showing "[消息已删除]".
- MEDIUM: upload failures showed raw untranslated SDK ctrl.text (e.g. "too
  large" instead of "文件大小超出限制") -- ported the old app's
  UPLOAD_CTRL_TEXT_CN table, which it built specifically because this
  native-protocol endpoint's errors never pass through the REST layer's
  own reason-code translation.
- Ambient SDK type corrections (tinode-sdk.d.ts): AccessMode.mode/given/want
  are numeric bitmasks at runtime, not the "JRWPS"-string type they were
  declared as (dormant today, nothing reads them yet, but wrong ahead of
  Phase 3's group-role logic); Drafty.sanitizeEntities's doc comment
  claimed a deep copy it doesn't do (verified it mutates entity .data in
  place); onAutoreconnectIteration's first param was misnamed "seconds"
  when the SDK always passes milliseconds.
- sendVoice() now passes `filename` to Drafty.insertAudio (was the only one
  of sendImage/sendFile/sendVoice omitting it).
- friends.ts's accept/reject-friend-request `version` param used a falsy
  check (`version ? ... : ...`) that would silently drop a legitimate `0`.

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

web/src/lib/api/client.ts

@@ -92,13 +92,13 @@ export function translateReason(reason: string | undefined, details?: unknown):
   return (typeof entry === 'function' ? entry(details) : entry) || null;
 }
 
-function requestId(): string {
+export function requestId(): string {
   return typeof crypto !== 'undefined' && crypto.randomUUID
     ? crypto.randomUUID()
     : `web_${Date.now().toString(36)}_${Math.random().toString(36).slice(2)}`;
 }
 
-function apiBase(): string {
+export function apiBase(): string {
   const endpoints = useSessionStore.getState().tenant?.endpoints;
   return (endpoints?.api || DEFAULT_API_BASE).replace(/\/$/, '');
 }