chore: remove dead code, add test infrastructure, update docs

- Delete 3 dead files: use-batch-processor.ts, use-i18n.ts, smart-crop.ts (AI package)
- Remove dead getJobProgress function and unused runPythonScript wrapper
- Remove 6 unused imports across API and web apps
- Remove unused shared types (ImageFormat, AppConfig, ApiError, HealthResponse, JobProgress)
  and constants (SUPPORTED_INPUT_FORMATS/OUTPUT_FORMATS, DEFAULT_OUTPUT_FORMAT)
- Remove unused store method (setOriginalBlobUrl) and clean AI package re-exports
- Add test infrastructure: vitest config, unit/integration/e2e tests, fixtures, screenshots
- Add Docker test infrastructure: Dockerfile.test, docker-compose.test.yml
- Add download_models.py for pre-baking AI model weights in Docker
- Add filename sanitization utility (apps/api/src/lib/filename.ts)
- Update .gitignore to exclude coverage/, *.tsbuildinfo, .superpowers/, test artifacts
- Update .dockerignore to exclude test/coverage/IDE artifacts from builds
- Update docs: remove smart crop from AI docs (uses Sharp directly), update bridge docs

tests/e2e/navigation.spec.ts

@@ -10,7 +10,15 @@ test.describe("Navigation", () => {
   test("sidebar Grid link goes to fullscreen view", async ({
     loggedInPage: page,
   }) => {
-    await page.locator("aside").getByText("Grid").click();
+    // Click the Grid link in the sidebar (links to /fullscreen)
+    const gridLink = page.locator("aside").getByText("Grid");
+    // If "Grid" text isn't directly visible (collapsed sidebar), try the link
+    if (await gridLink.isVisible({ timeout: 3000 }).catch(() => false)) {
+      await gridLink.click();
+    } else {
+      // Fallback: navigate via the href directly
+      await page.locator('aside a[href="/fullscreen"]').click();
+    }
     await expect(page).toHaveURL("/fullscreen");
   });