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/lib/auth/auth-context.test.tsx

@@ -12,7 +12,7 @@ vi.mock("../api/client", () => ({
 const { apiGet, apiPost } = await import("../api/client");
 
 // Test component that uses the auth context
-function TestComponent() {
+function TestComponent(): React.JSX.Element {
   const { user, isLoading, isAuthenticated, signOut } = useAuth();
 
   if (isLoading) {
@@ -40,7 +40,10 @@ describe("AuthContext", (): void => {
 
   it("should provide loading state initially", (): void => {
     vi.mocked(apiGet).mockImplementation(
-      () => new Promise(() => {}) // Never resolves
+      () =>
+        new Promise(() => {
+          // Never resolves - intentionally empty for testing loading state
+        })
     );
 
     render(
@@ -132,7 +135,9 @@ describe("AuthContext", (): void => {
 
   it("should throw error when useAuth is used outside AuthProvider", (): void => {
     // Suppress console.error for this test
-    const consoleErrorSpy = vi.spyOn(console, "error").mockImplementation(() => {});
+    const consoleErrorSpy = vi.spyOn(console, "error").mockImplementation(() => {
+      // Intentionally empty - suppressing React error boundary output
+    });
 
     expect(() => {
       render(<TestComponent />);