Add Docker Compose setup for web chat and email worker

Two services sharing a single image:
- web: Chainlit chat interface on port 8000
- email-worker: IMAP polling agent (main.py)

./data is mounted for persistent storage (registrations + conversations).
./openspec is mounted read-only so knowledge-base markdown files can be
edited on the host without rebuilding the image.

Configuration via .env (see .env.example).

https://claude.ai/code/session_015tJePX9eyQENYpJUF8XvvK

.dockerignore

@@ -0,0 +1,22 @@
+# Secrets — never bake into the image
+.env
+
+# Version control
+.git/
+.gitignore
+
+# Python build artefacts
+__pycache__/
+*.pyc
+*.pyo
+.pytest_cache/
+
+# Tests — not needed at runtime
+tests/
+
+# Persistent data — mounted as a volume at runtime
+data/
+
+# Tool configs — not needed in the container
+.claude/
+.gemini/