fix: Resolve web package lint and typecheck errors

Fixes ESLint and TypeScript errors in web package to pass CI checks:

- Fixed all Quality Rails violations (14 explicit any types)
- Fixed deprecated React event types (FormEvent → SyntheticEvent)
- Fixed 26 TypeScript errors (Promise types, test mocks, HTMLElement assertions)
- Added vitest DOM matcher type definitions
- Fixed unused variables and empty functions
- Resolved 43+ additional lint errors

Typecheck: ✅ 0 errors
Lint: 542 remaining (non-blocking in CI)

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

apps/web/src/hooks/__tests__/useLayouts.test.tsx

@@ -37,7 +37,7 @@ describe("useLayouts", (): void => {
       { id: "2", name: "Custom", isDefault: false, layout: [] },
     ];
 
-    (global.fetch as any).mockResolvedValueOnce({
+    (global.fetch as ReturnType<typeof vi.fn>).mockResolvedValueOnce({
       ok: true,
       json: () => mockLayouts,
     });
@@ -52,7 +52,7 @@ describe("useLayouts", (): void => {
   });
 
   it("should handle fetch errors", async (): Promise<void> => {
-    (global.fetch as any).mockRejectedValueOnce(new Error("API Error"));
+    (global.fetch as ReturnType<typeof vi.fn>).mockRejectedValueOnce(new Error("API Error"));
 
     const { result } = renderHook(() => useLayouts(), {
       wrapper: createWrapper(),
@@ -64,7 +64,7 @@ describe("useLayouts", (): void => {
   });
 
   it("should show loading state", (): void => {
-    (global.fetch as any).mockImplementation(() => new Promise(() => {}));
+    (global.fetch as ReturnType<typeof vi.fn>).mockImplementation(() => new Promise(() => {}));
 
     const { result } = renderHook(() => useLayouts(), {
       wrapper: createWrapper(),
@@ -87,7 +87,7 @@ describe("useCreateLayout", (): void => {
       layout: [],
     };
 
-    (global.fetch as any).mockResolvedValueOnce({
+    (global.fetch as ReturnType<typeof vi.fn>).mockResolvedValueOnce({
       ok: true,
       json: () => mockLayout,
     });
@@ -108,7 +108,7 @@ describe("useCreateLayout", (): void => {
   });
 
   it("should handle creation errors", async (): Promise<void> => {
-    (global.fetch as any).mockRejectedValueOnce(new Error("API Error"));
+    (global.fetch as ReturnType<typeof vi.fn>).mockRejectedValueOnce(new Error("API Error"));
 
     const { result } = renderHook(() => useCreateLayout(), {
       wrapper: createWrapper(),
@@ -138,7 +138,7 @@ describe("useUpdateLayout", (): void => {
       layout: [{ i: "widget-1", x: 0, y: 0, w: 2, h: 2 }],
     };
 
-    (global.fetch as any).mockResolvedValueOnce({
+    (global.fetch as ReturnType<typeof vi.fn>).mockResolvedValueOnce({
       ok: true,
       json: () => mockLayout,
     });
@@ -160,7 +160,7 @@ describe("useUpdateLayout", (): void => {
   });
 
   it("should handle update errors", async (): Promise<void> => {
-    (global.fetch as any).mockRejectedValueOnce(new Error("API Error"));
+    (global.fetch as ReturnType<typeof vi.fn>).mockRejectedValueOnce(new Error("API Error"));
 
     const { result } = renderHook(() => useUpdateLayout(), {
       wrapper: createWrapper(),
@@ -183,7 +183,7 @@ describe("useDeleteLayout", (): void => {
   });
 
   it("should delete a layout", async (): Promise<void> => {
-    (global.fetch as any).mockResolvedValueOnce({
+    (global.fetch as ReturnType<typeof vi.fn>).mockResolvedValueOnce({
       ok: true,
       json: () => ({ success: true }),
     });
@@ -200,7 +200,7 @@ describe("useDeleteLayout", (): void => {
   });
 
   it("should handle deletion errors", async (): Promise<void> => {
-    (global.fetch as any).mockRejectedValueOnce(new Error("API Error"));
+    (global.fetch as ReturnType<typeof vi.fn>).mockRejectedValueOnce(new Error("API Error"));
 
     const { result } = renderHook(() => useDeleteLayout(), {
       wrapper: createWrapper(),

apps/web/src/hooks/useWebSocket.test.tsx

@@ -17,14 +17,14 @@ describe("useWebSocket", (): void => {
     mockSocket = {
       on: vi.fn((event: string, handler: (...args: unknown[]) => void) => {
         eventHandlers[event] = handler;
-        return mockSocket as Socket;
+        return mockSocket;
       }) as unknown as Socket["on"],
       off: vi.fn((event?: string) => {
         if (event && Object.hasOwn(eventHandlers, event)) {
           // eslint-disable-next-line @typescript-eslint/no-dynamic-delete
           delete eventHandlers[event];
         }
-        return mockSocket as Socket;
+        return mockSocket;
       }) as unknown as Socket["off"],
       connect: vi.fn(),
       disconnect: vi.fn(),