implement demo mode

examples/demo/docker-compose.yml

@@ -0,0 +1,37 @@
+# Public demo of Ignis.
+#
+# - Vaults live on tmpfs (RAM-backed, transient by design)
+# - 20 MB total tmpfs, 700 KB per session, 3 vaults per session
+# - 30-minute inactivity timeout, in-process cleanup
+# - CORS proxy locked down to a known-safe domain allowlist
+# - Obsidian account login blocked (proxy + UI)
+
+services:
+  ignis-demo:
+    build:
+      context: ../..
+    ports:
+      - "8080:8080"
+    environment:
+      - DEMO_MODE=true
+      - DEMO_MAX_SESSIONS=20
+      - DEMO_VAULTS_PER_SESSION=3
+      - DEMO_SESSION_QUOTA_BYTES=716800 # 700 KB
+      - DEMO_TIMEOUT_MS=1800000 # 30 min
+      # Mount your own template at /app/demo-template to ship a richer
+      # starter vault without committing it to the repo. Defaults to the
+      # bundled server/demo-template/.
+      # - DEMO_TEMPLATE_DIR=/app/demo-template
+      - WRITE_COALESCE_MS=0 # tmpfs doesn't need debouncing
+      - PUID=1000
+      - PGID=1000
+    tmpfs:
+      - /vaults:size=20m,mode=1700
+    volumes:
+      - ./data:/app/data
+      - obsidian-app:/app/obsidian-app
+      # - ./my-demo-template:/app/demo-template:ro
+    restart: unless-stopped
+
+volumes:
+  obsidian-app: