Add /strip endpoint and web UI for metadata removal

- POST /strip: accepts any image, strips all metadata (EXIF, GPS, IPTC, XMP),
  returns clean anonymous JPEG at original dimensions (quality 92)
- GET / now serves a minimal web UI with drag-and-drop upload
- Token prompt on first use, saved to localStorage
- Add CLAUDE.md with project context

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

CLAUDE.md

@@ -0,0 +1,53 @@
+# PostConvert
+
+Image/PDF-to-JPEG conversion microservice. Single-file Node.js/Express app (`server.js`).
+
+## Tech Stack
+
+- Node.js 18+ (ES modules), Express
+- Sharp (image processing), libheif-js (HEIC/HEIF via WASM)
+- pdftoppm from Poppler (PDF rendering), archiver (ZIP output)
+- Docker (node:20-bookworm-slim), deployed on Fly.io (sjc region)
+
+## Endpoints
+
+- `GET /health` — health check
+- `POST /convert` — image or first PDF page → JPEG
+- `POST /convert/pdf` — all PDF pages → ZIP of JPEGs
+
+## Auth
+
+Bearer token via `CONVERTER_TOKEN` env var on all endpoints.
+
+## Key Design
+
+- Single-flight concurrency (1 conversion at a time, 429 if busy)
+- Resize/quality via headers: `x-jpeg-quality`, `x-max-dimension`, `x-pdf-dpi`, `x-without-enlargement`
+- Pixel limit 200M, bounded /tmp, no stack traces leaked, request timeouts
+- Fly.io auto-scaling 0–10 machines, 2 concurrent connection hard limit
+
+## Environment Variables
+
+- `PORT` (default 8080)
+- `CONVERTER_TOKEN` (required)
+- `REQ_TIMEOUT_MS` (default 120s, range 5–600s)
+- `REQ_TIMEOUT_PDF_MS` (default 5m, range 10s–30m)
+
+## Development
+
+```sh
+npm install
+node server.js
+```
+
+Docker:
+```sh
+docker build -t postconvert .
+docker run -e CONVERTER_TOKEN=secret -p 8080:8080 postconvert
+```
+
+## Fly.io Deployment
+
+Tokens are in `.env` (gitignored). Load with `source .env` or use `dotenv`.
+
+Deploy: `FLY_API_TOKEN="$FLY_API_TOKEN" fly deploy`