feat(web): discord-style chat, members pane, invitations and optimistic send [CI]

- chat: left-aligned discord-style messages with grouped senders, hover
  actions, an auto-growing composer and file cards
- send: render messages and files locally first and replace the
  placeholder when the worker publishes the real item; failures keep the
  text with a retry action
- navigation: space rail plus a flatter channel list with the space name
  header and collapsible groups
- members: right pane tabs (files / members) grouped by online, offline
  and pending users, with a prominent invite action and a top bar shortcut
- notifications: toast host for invite results; invitees get a toast with
  an accept action, and the invitation payload now carries the space name
  and inviter inside the encrypted grant
- users over devices: drop device names, the device list and device
  rename/release; senders show the account (guests show as guest) and the
  share panel only keeps links
- follow contract 7.0.0 (max_members, members_used, members_full, /join)
- docs: ui-design and frontend updated for the new layout and concepts

web/src/core-bridge/contract.test.ts

@@ -3,15 +3,16 @@ import { supportsApiContract } from './contract';
 
 describe('API contract compatibility', () => {
   it('accepts compatible SemVer releases in the supported major', () => {
-    expect(supportsApiContract('6.0.0')).toBe(true);
-    expect(supportsApiContract('6.8.2')).toBe(true);
-    expect(supportsApiContract('6.2.0-rc.1')).toBe(true);
+    expect(supportsApiContract('7.0.0')).toBe(true);
+    expect(supportsApiContract('7.8.2')).toBe(true);
+    expect(supportsApiContract('7.2.0-rc.1')).toBe(true);
   });
 
   it('rejects a breaking major and malformed versions', () => {
     expect(supportsApiContract('3.0.0')).toBe(false);
     expect(supportsApiContract('4.0.0')).toBe(false);
     expect(supportsApiContract('5.0.0')).toBe(false);
+    expect(supportsApiContract('6.1.0')).toBe(false);
     expect(supportsApiContract('01.0.0')).toBe(false);
     expect(supportsApiContract(undefined)).toBe(false);
   });