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/applications.rs

@@ -0,0 +1,107 @@
+// api/applications.rs — Server functions for applications and their port associations
+
+use leptos::prelude::*;
+
+use crate::models::Application;
+
+// ─── Queries ──────────────────────────────────────────────────────────────────
+
+/// Returns all applications ordered by name.
+#[server]
+pub async fn get_applications() -> Result<Vec<Application>, ServerFnError> {
+    use sqlx::AnyPool;
+    use crate::server::repository::applications as repo;
+
+    let pool = use_context::<AnyPool>()
+        .ok_or_else(|| ServerFnError::new("Database pool not found in context"))?;
+
+    repo::list_applications(&pool)
+        .await
+        .map_err(|e| ServerFnError::new(e.to_string()))
+}
+
+/// Returns the port numbers associated with an application.
+#[server]
+pub async fn get_ports_for_application(
+    application_id: i64,
+) -> Result<Vec<u16>, ServerFnError> {
+    use sqlx::AnyPool;
+    use crate::server::repository::applications as repo;
+
+    let pool = use_context::<AnyPool>()
+        .ok_or_else(|| ServerFnError::new("Database pool not found in context"))?;
+
+    repo::list_ports_for_application(&pool, application_id)
+        .await
+        .map_err(|e| ServerFnError::new(e.to_string()))
+}
+
+// ─── Mutations ────────────────────────────────────────────────────────────────
+
+/// Creates a new application and returns the created record.
+#[server]
+pub async fn create_application(name: String) -> Result<Application, ServerFnError> {
+    use sqlx::AnyPool;
+    use crate::server::repository::applications as repo;
+
+    let pool = use_context::<AnyPool>()
+        .ok_or_else(|| ServerFnError::new("Database pool not found in context"))?;
+
+    repo::create_application(&pool, &name)
+        .await
+        .map_err(|e| ServerFnError::new(e.to_string()))
+}
+
+/// Deletes an application and all its port associations.
+///
+/// Returns `true` if the application existed and was deleted.
+#[server]
+pub async fn delete_application(id: i64) -> Result<bool, ServerFnError> {
+    use sqlx::AnyPool;
+    use crate::server::repository::applications as repo;
+
+    let pool = use_context::<AnyPool>()
+        .ok_or_else(|| ServerFnError::new("Database pool not found in context"))?;
+
+    repo::delete_application(&pool, id)
+        .await
+        .map_err(|e| ServerFnError::new(e.to_string()))
+}
+
+/// Associates a port number with an application.
+///
+/// If the association already exists, this is a no-op.
+#[server]
+pub async fn add_port_to_application(
+    application_id: i64,
+    port_number: u16,
+) -> Result<(), ServerFnError> {
+    use sqlx::AnyPool;
+    use crate::server::repository::applications as repo;
+
+    let pool = use_context::<AnyPool>()
+        .ok_or_else(|| ServerFnError::new("Database pool not found in context"))?;
+
+    repo::add_port_to_application(&pool, application_id, port_number)
+        .await
+        .map_err(|e| ServerFnError::new(e.to_string()))
+}
+
+/// Removes a port association from an application.
+///
+/// If the association does not exist, this is a no-op.
+#[server]
+pub async fn remove_port_from_application(
+    application_id: i64,
+    port_number: u16,
+) -> Result<(), ServerFnError> {
+    use sqlx::AnyPool;
+    use crate::server::repository::applications as repo;
+
+    let pool = use_context::<AnyPool>()
+        .ok_or_else(|| ServerFnError::new("Database pool not found in context"))?;
+
+    repo::remove_port_from_application(&pool, application_id, port_number)
+        .await
+        .map_err(|e| ServerFnError::new(e.to_string()))
+}