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/CalendarWidget.tsx

@@ -15,7 +15,7 @@ interface Event {
   allDay: boolean;
 }
 
-export function CalendarWidget({ id: _id, config: _config }: WidgetProps) {
+export function CalendarWidget({ id: _id, config: _config }: WidgetProps): React.JSX.Element {
   const [events, setEvents] = useState<Event[]>([]);
   const [isLoading, setIsLoading] = useState(true);
 
@@ -57,7 +57,7 @@ export function CalendarWidget({ id: _id, config: _config }: WidgetProps) {
     }, 500);
   }, []);
 
-  const formatTime = (dateString: string) => {
+  const formatTime = (dateString: string): string => {
     const date = new Date(dateString);
     return date.toLocaleTimeString("en-US", {
       hour: "numeric",
@@ -66,7 +66,7 @@ export function CalendarWidget({ id: _id, config: _config }: WidgetProps) {
     });
   };
 
-  const formatDay = (dateString: string) => {
+  const formatDay = (dateString: string): string => {
     const date = new Date(dateString);
     const today = new Date();
     const tomorrow = new Date(today);
@@ -80,7 +80,7 @@ export function CalendarWidget({ id: _id, config: _config }: WidgetProps) {
     return date.toLocaleDateString("en-US", { weekday: "short", month: "short", day: "numeric" });
   };
 
-  const getUpcomingEvents = () => {
+  const getUpcomingEvents = (): Event[] => {
     const now = new Date();
     return events
       .filter((e) => new Date(e.startTime) > now)