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/components/knowledge/__tests__/EntryEditor.test.tsx

@@ -31,7 +31,7 @@ describe("EntryEditor", (): void => {
     const content = "# Test Content\n\nThis is a test.";
     render(<EntryEditor {...defaultProps} content={content} />);
 
-    const textarea = screen.getByPlaceholderText(/Write your content here/);
+    const textarea = screen.getByPlaceholderText(/Write your content here/) as HTMLTextAreaElement;
     expect(textarea.value).toBe(content);
   });
 
@@ -112,7 +112,7 @@ describe("EntryEditor", (): void => {
     render(<EntryEditor {...defaultProps} content={content} />);
 
     // Verify content in edit mode
-    const textarea = screen.getByPlaceholderText(/Write your content here/);
+    const textarea = screen.getByPlaceholderText(/Write your content here/) as HTMLTextAreaElement;
     expect(textarea.value).toBe(content);
 
     // Toggle to preview
@@ -121,7 +121,7 @@ describe("EntryEditor", (): void => {
 
     // Toggle back to edit
     await user.click(screen.getByText("Edit"));
-    const textareaAfter = screen.getByPlaceholderText(/Write your content here/);
+    const textareaAfter = screen.getByPlaceholderText(/Write your content here/) as HTMLTextAreaElement;
     expect(textareaAfter.value).toBe(content);
   });
 

apps/web/src/components/knowledge/__tests__/LinkAutocomplete.test.tsx

@@ -380,7 +380,12 @@ describe("LinkAutocomplete", (): void => {
     const searchPromise = new Promise((resolve) => {
       resolveSearch = resolve;
     });
-    mockApiGet.mockReturnValue(searchPromise as Promise<any>);
+    mockApiGet.mockReturnValue(
+      searchPromise as Promise<{
+        data: unknown[];
+        meta: { total: number; page: number; limit: number; totalPages: number };
+      }>
+    );
 
     render(<LinkAutocomplete textareaRef={textareaRef} onInsert={onInsertMock} />);