feat(chat): rich shared-media view, status selector, drag-drop upload + fixes

Chat / shared media:
- Media/Docs/Links: clean underline tabs (green active), audio & video now
  classified as Media and rendered as tiles (download + headphone/play +
  duration) instead of broken-image glyphs; image thumbnails -> lightbox
- Drag-and-drop a file/video/image onto a conversation to send it
- Fix: removed #chatPanel{position:relative} override that collapsed the
  conversation pane (messages spilled into a clipped right-edge strip)
- "Media, links & docs" row cleaned up (no folder/placeholder icon); media
  popup keeps the back arrow, drops the redundant close button

Presence / status:
- Single current-status row with an arrow that expands Available/Away/On leave
- On leave = circle with minus, In a call = solid red indicators
- Fix: selected-status tick now follows the chosen option

Icons: added headphones + play; bumped icons.js cache-bust to v4

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

server/public/sw.js

@@ -1,4 +1,4 @@
-// BizGaze Connect service worker — NOTIFICATIONS ONLY.
+// Biz Connect service worker — NOTIFICATIONS ONLY.
 // Intentionally has NO 'fetch' handler and NO caching, so it can never serve a stale
 // version of the app. Its only job is to show push notifications when the page is in
 // the background / frozen / closed, and to open the right chat when one is clicked.
@@ -12,7 +12,7 @@ self.addEventListener('fetch', () => {});
 self.addEventListener('push', (event) => {
   let d = {};
   try { d = event.data ? event.data.json() : {}; } catch (_) {}
-  const title = d.title || 'BizGaze Connect';
+  const title = d.title || 'Biz Connect';
   const options = {
     body: d.body || '',
     icon: '/logo.png',