feat: add Docker support with multi-stage build and compose profiles

Multi-stage Dockerfile (base/dev/prod) using uv for fast installs.
Dev stage supports hot-reload via bind-mounted source; prod stage
builds an optimised image with 4 uvicorn workers. docker-compose.yml
provides 'dev' and 'prod' profiles with named volumes for data.

docker-compose.yml

@@ -0,0 +1,34 @@
+services:
+  app:
+    build:
+      context: .
+      target: prod
+    ports:
+      - "8000:8000"
+    environment:
+      OIDC_OP_ISSUER: "http://localhost:8000"
+      OIDC_OP_SESSION_SECRET: "change-me-in-production"
+    volumes:
+      - app-data:/app/data
+    profiles:
+      - prod
+
+  app-dev:
+    build:
+      context: .
+      target: dev
+    ports:
+      - "8000:8000"
+    environment:
+      OIDC_OP_ISSUER: "http://localhost:8000"
+      OIDC_OP_DEBUG: "true"
+    volumes:
+      - ./src:/app/src
+      - ./pyproject.toml:/app/pyproject.toml
+      - dev-data:/app/data
+    profiles:
+      - dev
+
+volumes:
+  app-data:
+  dev-data: