feat(fase-17): ChangelogModal component + unit tests

ChangelogModal renders the repo-root CHANGELOG.md (bundled at build
time via Vite's ?raw query, 5 levels up from the component file) in
an overlay+panel modal. Markdown is parsed inline (`#`/`##`/`###`
headers, `-`/`*` lists, `**bold**`) with HTML-escape on every input
line — input is static repo content so the surface is closed.

Esc and overlay-click both call `onClose`. The keydown listener is
attached only while `open` is true via a $effect.

Three new Paraglide messages (en/es): `settings_about_view_changelog`,
`changelog_modal_title`, `changelog_modal_close`.

Unit tests (CHM-U-01..04) follow the Spinner.test.ts pattern (Svelte 5
mount/unmount + flushSync for the Escape spec).

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

apps/web/src/lib/components/ChangelogModal.test.ts

@@ -0,0 +1,77 @@
+/**
+ * Fase 17.4.1 — ChangelogModal unit tests.
+ *
+ * Mirrors the Spinner.test.ts pattern (Svelte 5 `mount`/`unmount`, no
+ * @testing-library dependency). The modal imports CHANGELOG.md via Vite's
+ * `?raw` query — vitest runs against the same Vite config (see
+ * apps/web/vitest.config.ts) so the import resolves to the file contents at
+ * test time.
+ *
+ * Specs:
+ *   CHM-U-01 — `open={false}` renders nothing.
+ *   CHM-U-02 — `open={true}` renders the CHANGELOG `<h1>`.
+ *   CHM-U-03 — click on the overlay fires `onClose`.
+ *   CHM-U-04 — pressing Escape fires `onClose`.
+ */
+import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest';
+import { flushSync, mount, unmount } from 'svelte';
+import ChangelogModal from './ChangelogModal.svelte';
+
+let host: HTMLElement;
+// eslint-disable-next-line @typescript-eslint/no-explicit-any
+let instance: any;
+
+function render(props: Record<string, unknown>) {
+	host = document.createElement('div');
+	document.body.appendChild(host);
+	instance = mount(ChangelogModal, { target: host, props });
+	return host;
+}
+
+beforeEach(() => {
+	host = document.createElement('div');
+});
+
+afterEach(() => {
+	if (instance) unmount(instance);
+	if (host?.parentNode) host.parentNode.removeChild(host);
+	instance = null;
+});
+
+describe('ChangelogModal component', () => {
+	it('CHM-U-01: open=false renders nothing visible', () => {
+		const root = render({ open: false, onClose: () => {} });
+		expect(root.querySelector('[data-testid="changelog-modal"]')).toBeNull();
+	});
+
+	it('CHM-U-02: open=true renders the CHANGELOG h1 heading', () => {
+		const root = render({ open: true, onClose: () => {} });
+		const modal = root.querySelector('[data-testid="changelog-modal"]');
+		expect(modal).not.toBeNull();
+		const h1 = modal?.querySelector('h1');
+		expect(h1).not.toBeNull();
+		expect(h1?.textContent?.trim()).toBe('Changelog');
+	});
+
+	it('CHM-U-03: click on overlay fires onClose', () => {
+		const onClose = vi.fn();
+		const root = render({ open: true, onClose });
+		const overlay = root.querySelector('[data-testid="changelog-modal-overlay"]') as
+			| HTMLElement
+			| null;
+		expect(overlay).not.toBeNull();
+		overlay?.dispatchEvent(new MouseEvent('click', { bubbles: true }));
+		expect(onClose).toHaveBeenCalledTimes(1);
+	});
+
+	it('CHM-U-04: Escape key fires onClose', () => {
+		const onClose = vi.fn();
+		render({ open: true, onClose });
+		// $effect runs in a microtask after mount. flushSync drains pending
+		// reactive effects so the keydown listener is attached before we
+		// dispatch the event.
+		flushSync();
+		window.dispatchEvent(new KeyboardEvent('keydown', { key: 'Escape' }));
+		expect(onClose).toHaveBeenCalledTimes(1);
+	});
+});