chore: initialise la structure du projet SentinelMesh

- Workspace Cargo avec backend, agent-scan-network, agent-metric
- Skeleton Rust pour les trois crates (Axum, Tokio, SQLx)
- Documentation : README, FEATURES, ROADMAP, ARCHITECTURE, API, INSTALL
- Exemples de widgets Glance (custom-api)
- Script d'installation agents (squelette Phase 5)
- Docker Compose + Dockerfile backend
- .gitignore et CLAUDE.md

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

docker-compose.yml

@@ -0,0 +1,14 @@
+services:
+  backend:
+    build: ./backend
+    ports:
+      - "8080:8080"
+    volumes:
+      - sentinelmesh-data:/data
+    environment:
+      DATABASE_URL: sqlite:///data/sentinelmesh.sqlite
+      RUST_LOG: info
+    restart: unless-stopped
+
+volumes:
+  sentinelmesh-data: