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/hooks/__tests__/useLayouts.test.tsx

@@ -21,7 +21,7 @@ const createWrapper = () => {
     },
   });
 
-  return ({ children }: { children: ReactNode }) => (
+  return ({ children }: { children: ReactNode }): React.JSX.Element => (
     <QueryClientProvider client={queryClient}>{children}</QueryClientProvider>
   );
 };
@@ -64,7 +64,12 @@ describe("useLayouts", (): void => {
   });
 
   it("should show loading state", (): void => {
-    (global.fetch as ReturnType<typeof vi.fn>).mockImplementation(() => new Promise(() => {}));
+    (global.fetch as ReturnType<typeof vi.fn>).mockImplementation(
+      () =>
+        new Promise((): void => {
+          // Intentionally empty to keep promise pending
+        })
+    );
 
     const { result } = renderHook(() => useLayouts(), {
       wrapper: createWrapper(),