feat(frontend): merge top-bar search with the filter bar, expose kind/created filters

Unify the upstream top-bar search box and the local SearchFilterBar into
one filtering capability sharing a single state store, with the URL as
its projection:

- lib/stores/filter.svelte.ts: module-level $state store, the single
  source of truth; every surface mutates the same proxy in place
- lib/composables/useFilterUrlSync.svelte.ts: one $effect serves both
  directions (URL -> store adoption, store -> URL replaceState write)
  with echo suppression so the loop settles in one round-trip
- FilterFields.svelte: the five selects (type/size/modified/created/
  kind) + recursive switch; word lists and i18n labels live in one
  place; SearchFilterBar reuses it instead of its own copies
- TopBarFilterPanel.svelte: dropdown panel anchored inside the top-bar
  search input (in-field toggle button with active-count badge);
  Escape/outside-click close, no overlay stacking with suggestions
- FilterChips.svelte: dismissible chips on /search, which is now
  URL-driven and loses its three inline <select>s
- New dimensions the backend already supported: kind (file/folder,
  resource_types) and created (created_after); URL keys q/type/size/
  date/created/kind/recursive, non-defaults only, unknown values
  degrade to defaults
- /files keeps in-place filtering (no navigation); folderTarget
  carries filter params through folder entry; ?file= and in/scope
  survive filter writes
- topbar.css: input right padding reserves the three in-field controls

Backend unchanged.

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

frontend/src/routes/files/page.test.ts

@@ -321,3 +321,41 @@ it('shows the search result count while the filter is active', async () => {
 	const stat = await screen.findByTestId('files-folder-stat');
 	expect(stat.textContent).toContain('1 results');
 });
+
+it('hydrates filter presets from a deep-linked URL and runs the scoped search', async () => {
+	withListing();
+	pageState.url = new URL('http://localhost/files/home?type=image&kind=folder');
+	m(searchResources).mockResolvedValue({ items: [], query_time_ms: 1 });
+	render(FilesPage);
+	await waitFor(() => expect(fetchFolderPage).toHaveBeenCalled());
+	await waitFor(() => expect(searchResources).toHaveBeenCalled());
+	expect(m(searchResources).mock.calls[0][1]).toMatchObject({
+		folderId: 'home',
+		fileTypes: ['jpg', 'jpeg', 'png', 'gif', 'webp', 'svg', 'bmp', 'heic', 'avif', 'tiff'],
+		resourceTypes: ['folder']
+	});
+	// The bar's own select reflects the hydrated state (expand the row first).
+	await fireEvent.click(screen.getByTestId('filter-advanced-toggle-btn'));
+	expect((screen.getByTestId('filter-type-select') as HTMLSelectElement).value).toBe('image');
+});
+
+it('writes an edited filter back to the URL exactly once (no sync loop)', async () => {
+	withListing();
+	m(searchResources).mockResolvedValue({ items: [], query_time_ms: 1 });
+	render(FilesPage);
+	await waitFor(() => expect(fetchFolderPage).toHaveBeenCalled());
+	m(goto).mockClear();
+	vi.useFakeTimers();
+	await fireEvent.input(screen.getByTestId('filter-keyword-input'), {
+		target: { value: 'hello' }
+	});
+	await vi.advanceTimersByTimeAsync(400);
+	vi.useRealTimers();
+	// One replaceState write for the debounced keyword — and nothing else:
+	// the effect must recognize its own write and settle, not ping-pong.
+	expect(goto).toHaveBeenCalledTimes(1);
+	// The sync composable passes a path/search/hash string (a URL instance
+	// would trip svelte/prefer-svelte-reactivity in the .svelte.ts module).
+	const written = m(goto).mock.calls[0][0] as string;
+	expect(written).toContain('q=hello');
+});