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/app/(authenticated)/tasks/page.test.tsx

@@ -4,7 +4,7 @@ import TasksPage from "./page";
 
 // Mock the TaskList component
 vi.mock("@/components/tasks/TaskList", () => ({
-  TaskList: ({ tasks, isLoading }: { tasks: unknown[]; isLoading: boolean }) => (
+  TaskList: ({ tasks, isLoading }: { tasks: unknown[]; isLoading: boolean }): React.JSX.Element => (
     <div data-testid="task-list">{isLoading ? "Loading" : `${String(tasks.length)} tasks`}</div>
   ),
 }));