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>

src/server/db.rs

@@ -0,0 +1,68 @@
+// server/db.rs — Database connection pool and migrations
+//
+// This module provides two functions called once at server startup:
+//   - `create_pool`    : opens a connection pool to the database
+//   - `run_migrations` : applies all pending SQL migrations
+//
+// `AnyPool` lets the same Rust code target both SQLite (dev) and
+// PostgreSQL (production) — only DATABASE_URL changes.
+
+use sqlx::AnyPool;
+use thiserror::Error;
+
+use crate::server::config::{AppConfig, DatabaseBackend};
+
+// ─── Errors ───────────────────────────────────────────────────────────────────
+
+#[derive(Debug, Error)]
+pub enum DbError {
+    #[error("Database connection failed: {0}")]
+    Connection(#[from] sqlx::Error),
+
+    #[error("Migration failed: {0}")]
+    Migration(#[from] sqlx::migrate::MigrateError),
+}
+
+// ─── Pool creation ────────────────────────────────────────────────────────────
+
+/// Opens a connection pool to the database specified in `config.database_url`.
+///
+/// A pool maintains multiple open connections so concurrent requests
+/// do not block each other waiting for a single connection.
+///
+/// `install_default_drivers()` must be called before `AnyPool::connect`
+/// to register both the SQLite and PostgreSQL drivers in the `Any` registry.
+pub async fn create_pool(config: &AppConfig) -> Result<AnyPool, DbError> {
+    // Register SQLite and PostgreSQL drivers so `AnyPool` can dispatch
+    // to the correct one based on the URL scheme (sqlite:// vs postgres://).
+    sqlx::any::install_default_drivers();
+
+    let pool = AnyPool::connect(&config.database_url).await?;
+    Ok(pool)
+}
+
+// ─── Migrations ───────────────────────────────────────────────────────────────
+
+/// Applies all pending migrations from the directory matching the active backend.
+///
+/// Two separate directories handle SQL syntax differences:
+///   - `migrations/sqlite/`   : uses `INTEGER PRIMARY KEY AUTOINCREMENT`
+///   - `migrations/postgres/` : uses `BIGSERIAL PRIMARY KEY`
+///
+/// SQLx tracks applied migrations in a `_sqlx_migrations` table, so running
+/// this function on an already-migrated database is always safe (idempotent).
+///
+/// `sqlx::migrate!("path")` is a compile-time macro: it embeds all `.sql`
+/// files from the given path directly into the binary. The path is relative
+/// to the project root (where Cargo.toml lives).
+pub async fn run_migrations(pool: &AnyPool, backend: &DatabaseBackend) -> Result<(), DbError> {
+    match backend {
+        DatabaseBackend::Sqlite => {
+            sqlx::migrate!("migrations/sqlite").run(pool).await?;
+        }
+        DatabaseBackend::Postgres => {
+            sqlx::migrate!("migrations/postgres").run(pool).await?;
+        }
+    }
+    Ok(())
+}

src/server/mod.rs

@@ -11,5 +11,11 @@ pub mod routes;
 #[cfg(feature = "ssr")]
 pub mod config;
 
+#[cfg(feature = "ssr")]
+pub mod db;
+
+#[cfg(feature = "ssr")]
+pub mod state;
+
 #[cfg(feature = "ssr")]
 pub mod validation;

src/server/state.rs

@@ -0,0 +1,42 @@
+// server/state.rs — Shared Axum application state
+//
+// Axum uses a typed state system: any handler can extract a specific type
+// from the shared state using the `State<T>` extractor.
+//
+// We store two pieces of state:
+//   - `leptos_options` : required by Leptos SSR routes
+//   - `db`             : database pool shared across all requests
+
+use axum::extract::FromRef;
+use leptos::config::LeptosOptions;
+use sqlx::AnyPool;
+
+// ─── AppState ─────────────────────────────────────────────────────────────────
+
+/// Shared state available to every Axum handler and Leptos server function.
+///
+/// `#[derive(Clone)]` is required by Axum: each request receives its own clone.
+/// Both fields are cheap to clone — they hold reference-counted pointers
+/// under the hood, so cloning just increments an atomic counter.
+#[derive(Clone)]
+pub struct AppState {
+    /// Leptos configuration (output paths, site address, reload port…).
+    pub leptos_options: LeptosOptions,
+
+    /// Shared connection pool to the database.
+    /// Using a pool (not a single connection) allows concurrent requests
+    /// to run their queries in parallel without contention.
+    pub db: AnyPool,
+}
+
+// ─── FromRef implementations ──────────────────────────────────────────────────
+
+/// Tells Axum how to extract just `LeptosOptions` from the full `AppState`.
+///
+/// `.leptos_routes()` in main.rs requires this impl because it stores
+/// only `LeptosOptions` internally, not the full application state.
+impl FromRef<AppState> for LeptosOptions {
+    fn from_ref(state: &AppState) -> Self {
+        state.leptos_options.clone()
+    }
+}