feat(networks): add network detail page with paginated host list and contextual back button

- API: add get_network(id) server function
- NetworkDetailPage at /networks/:id — network name + CIDR header, paginated
  host table (Name, IP, Ports, Apps) linking to /hosts/:id?back=/networks/:id
- Networks list: make network name a link to its detail page
- HostDetailPage: read ?back= query param to show "← Network" or "← Hosts"
  and navigate to the correct destination

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

src/api/networks.rs

@@ -77,6 +77,21 @@ pub async fn get_networks_with_counts() -> Result<Vec<NetworkWithCounts>, Server
     Ok(networks)
 }
 
+/// Returns a single network by id, or an error if it does not exist.
+#[server]
+pub async fn get_network(id: i64) -> Result<Network, ServerFnError> {
+    use sqlx::AnyPool;
+    use crate::server::repository::networks as repo;
+
+    let pool = use_context::<AnyPool>()
+        .ok_or_else(|| ServerFnError::new("Database pool not found in context"))?;
+
+    repo::find_network(&pool, id)
+        .await
+        .map_err(|e| ServerFnError::new(e.to_string()))?
+        .ok_or_else(|| ServerFnError::new(format!("Network {id} not found")))
+}
+
 // ─── Mutations ────────────────────────────────────────────────────────────────
 
 /// Creates a new network with the given name and CIDR block.