fix: Resolve all ESLint errors and warnings in web package

Fixes all 542 ESLint problems in the web package to achieve 0 errors and 0 warnings.

Changes:
- Fixed 144 issues: nullish coalescing, return types, unused variables
- Fixed 118 issues: unnecessary conditions, type safety, template literals
- Fixed 79 issues: non-null assertions, unsafe assignments, empty functions
- Fixed 67 issues: explicit return types, promise handling, enum comparisons
- Fixed 45 final warnings: missing return types, optional chains
- Fixed 25 typecheck-related issues: async/await, type assertions, formatting
- Fixed JSX.Element namespace errors across 90+ files

All Quality Rails violations resolved. Lint and typecheck both pass with 0 problems.

Files modified: 118 components, tests, hooks, and utilities

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

apps/web/src/components/widgets/AgentStatusWidget.tsx

@@ -15,7 +15,7 @@ interface Agent {
   taskCount: number;
 }
 
-export function AgentStatusWidget({ id: _id, config: _config }: WidgetProps) {
+export function AgentStatusWidget({ id: _id, config: _config }: WidgetProps): React.JSX.Element {
   const [agents, setAgents] = useState<Agent[]>([]);
   const [isLoading, setIsLoading] = useState(true);
 
@@ -52,7 +52,7 @@ export function AgentStatusWidget({ id: _id, config: _config }: WidgetProps) {
     }, 500);
   }, []);
 
-  const getStatusIcon = (status: Agent["status"]) => {
+  const getStatusIcon = (status: Agent["status"]): React.JSX.Element => {
     switch (status) {
       case "WORKING":
         return <Activity className="w-4 h-4 text-blue-500 animate-pulse" />;
@@ -69,19 +69,19 @@ export function AgentStatusWidget({ id: _id, config: _config }: WidgetProps) {
     }
   };
 
-  const getStatusText = (status: Agent["status"]) => {
+  const getStatusText = (status: Agent["status"]): string => {
     return status.charAt(0).toUpperCase() + status.slice(1).toLowerCase();
   };
 
-  const getTimeSinceLastHeartbeat = (timestamp: string) => {
+  const getTimeSinceLastHeartbeat = (timestamp: string): string => {
     const now = new Date();
     const last = new Date(timestamp);
     const diffMs = now.getTime() - last.getTime();
 
     if (diffMs < 60000) return "Just now";
-    if (diffMs < 3600000) return `${Math.floor(diffMs / 60000)}m ago`;
-    if (diffMs < 86400000) return `${Math.floor(diffMs / 3600000)}h ago`;
-    return `${Math.floor(diffMs / 86400000)}d ago`;
+    if (diffMs < 3600000) return `${String(Math.floor(diffMs / 60000))}m ago`;
+    if (diffMs < 86400000) return `${String(Math.floor(diffMs / 3600000))}h ago`;
+    return `${String(Math.floor(diffMs / 86400000))}d ago`;
   };
 
   const stats = {