feat(api): add Leptos server functions bridging client and server

- Add src/api/ module with server functions for networks, hosts, applications
- Each server function retrieves the pool via use_context::<AnyPool>()
- Pool is injected via provide_context in two places in main.rs:
  * leptos_routes_with_context: for SSR renders and inline server fn calls
  * handle_server_fns_with_context on /api/*fn_name: for WASM client calls
- create_host validates IP against network CIDR before inserting
- create_network validates CIDR format before inserting

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

src/api/mod.rs

@@ -0,0 +1,19 @@
+// api/ — Leptos server functions (the bridge between client and server)
+//
+// Server functions are annotated with `#[server]`.
+// Leptos compiles them differently depending on the active feature:
+//
+//   ssr     → the function body runs on the server (normal async Rust code)
+//   hydrate → the body is replaced by an HTTP POST call to /api/<fn-name>
+//
+// This means:
+//   - Function signatures (arguments + return types) must compile for BOTH targets.
+//     All types used here must also be in `models.rs` (shared code).
+//   - Imports inside the function body are only compiled for `ssr`,
+//     so ssr-only modules (server::repository, sqlx) can be used freely there.
+//   - The pool is retrieved via `use_context::<AnyPool>()` — it is injected
+//     into the Leptos context by `main.rs` for every request.
+
+pub mod applications;
+pub mod hosts;
+pub mod networks;