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

apps/web/src/stores/file-store.ts

@@ -15,7 +15,6 @@ interface FileState {
   setFiles: (files: File[]) => void;
   setJobId: (id: string) => void;
   setProcessedUrl: (url: string | null) => void;
-  setOriginalBlobUrl: (url: string | null) => void;
   setProcessing: (v: boolean) => void;
   setError: (e: string | null) => void;
   setSizes: (original: number, processed: number) => void;
@@ -53,7 +52,6 @@ export const useFileStore = create<FileState>((set, get) => ({
   },
   setJobId: (id) => set({ jobId: id }),
   setProcessedUrl: (url) => set({ processedUrl: url }),
-  setOriginalBlobUrl: (url) => set({ originalBlobUrl: url }),
   setProcessing: (v) => set({ processing: v }),
   setError: (e) => set({ error: e, processing: false }),
   setSizes: (original, processed) =>