Extract severity color map into shared module

Severity-to-color mapping was duplicated in SeverityBadge, Tickets,
and MyTickets. Consolidated into lib/severityColors.ts with both
solid-bg (for stripes) and badge-style (for badges) variants.

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

client/src/pages/MyTickets.tsx

@@ -6,6 +6,7 @@ import SeverityBadge from '../components/SeverityBadge';
 import StatusBadge from '../components/StatusBadge';
 import { useTickets } from '../api/queries';
 import { useAuth } from '../contexts/AuthContext';
+import { SEVERITY_BG } from '../lib/severityColors';
 
 export default function MyTickets() {
   const { user } = useAuth();
@@ -42,17 +43,7 @@ export default function MyTickets() {
               className="flex items-center gap-4 bg-gray-900 border border-gray-800 rounded-lg px-4 py-3 hover:border-indigo-500/50 transition-all group"
             >
               <div
-                className={`w-1 self-stretch rounded-full flex-shrink-0 ${
-                  ticket.severity === 1
-                    ? 'bg-red-500'
-                    : ticket.severity === 2
-                      ? 'bg-orange-400'
-                      : ticket.severity === 3
-                        ? 'bg-yellow-400'
-                        : ticket.severity === 4
-                          ? 'bg-blue-400'
-                          : 'bg-gray-600'
-                }`}
+                className={`w-1 self-stretch rounded-full flex-shrink-0 ${SEVERITY_BG[ticket.severity] ?? 'bg-gray-600'}`}
               />
 
               <div className="flex-1 min-w-0">