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/BaseWidget.tsx

@@ -33,7 +33,7 @@ export function BaseWidget({
   className,
   isLoading = false,
   error,
-}: BaseWidgetProps) {
+}: BaseWidgetProps): React.JSX.Element {
   return (
     <div
       data-widget-id={id}
@@ -50,7 +50,7 @@ export function BaseWidget({
         </div>
 
         {/* Control buttons - only show if handlers provided */}
-        {(onEdit || onRemove) && (
+        {(onEdit ?? onRemove) && (
           <div className="flex items-center gap-1 ml-2">
             {onEdit && (
               <button