feat(db): add SQLx migrations and AppState with connection pool

- Add sqlx 0.8 (AnyPool, runtime-tokio, sqlite, postgres, migrate)
- Create 6 migration files for both SQLite and PostgreSQL backends
- Add server/db.rs: create_pool and run_migrations helpers
- Add server/state.rs: AppState with LeptosOptions + AnyPool
- Run migrations at server startup before accepting requests
- Fix Port model: remove host_id (ports are now a global catalog)
- Add HostPort join struct for the host_ports many-to-many table

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

Cargo.toml

@@ -21,6 +21,7 @@ ssr = [
     "dep:tracing-subscriber",
     "dep:dotenvy",
     "dep:ipnetwork",
+    "dep:sqlx",
     "leptos/ssr",
     "leptos_meta/ssr",
     "leptos_router/ssr",
@@ -68,6 +69,9 @@ tracing-subscriber = { version = "0.3", features = ["env-filter"], optional = tr
 dotenvy = { version = "0.15", optional = true }
 # Parsing et calcul de plages d'adresses IP (CIDR) — ex: 192.168.1.0/24
 ipnetwork = { version = "0.20", optional = true }
+# Database access: connection pools, queries, migrations — SQLite + PostgreSQL
+# "any" = runtime-dispatched driver (same code works with both backends)
+sqlx = { version = "0.8", features = ["runtime-tokio", "tls-rustls", "sqlite", "postgres", "migrate", "any"], optional = true }
 
 # --- Dépendances client uniquement (activées par la feature "hydrate") ---