Dark theme, roles overhaul, modal New Ticket, My Tickets page, and more

- Dark UI across all pages and components (gray-950/900/800 palette)
- New Ticket is now a centered modal (triggered from sidebar), not a separate page
- Add USER role: view and comment only; AGENT and SERVICE can create/edit tickets
- Only admins can set ticket status to CLOSED (enforced server + UI)
- Add My Tickets page (/my-tickets) showing tickets assigned to current user
- Add queue (category) filter to Dashboard
- Audit log entries are clickable to expand detail; comment body shown as markdown
- Resolved date now includes time (HH:mm) in ticket sidebar
- Store comment body in audit log detail for COMMENT_ADDED and COMMENT_DELETED
- Clarify role descriptions in Admin Users modal
- Remove CI/CD section from README; add full API reference documentation

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

server/src/middleware/auth.ts

@@ -55,3 +55,15 @@ export const requireAdmin = (
   }
   next()
 }
+
+// Blocks USER role — allows ADMIN, AGENT, SERVICE
+export const requireAgent = (
+  req: AuthRequest,
+  res: Response,
+  next: NextFunction
+) => {
+  if (req.user?.role === 'USER') {
+    return res.status(403).json({ error: 'Insufficient permissions' })
+  }
+  next()
+}