fix: add connection test feedback in server form

- Show error message when connection test fails
- Disable test button while testing
- Provide clear feedback when API key or hostname are invalid
- Reset error message on successful connection

Sources/Views/ServerFormView.swift

@@ -20,6 +20,8 @@ struct ServerFormView: View {
     @State private var hostname: String
     @State private var apiKey: String
     @State private var connectionOK: Bool = false
+    @State private var testingConnection: Bool = false
+    @State private var connectionError: String = ""
 
     @Environment(\.dismiss) private var dismiss
     
@@ -55,6 +57,12 @@ struct ServerFormView: View {
             SecureField("API Key", text: $apiKey)
                 .textFieldStyle(RoundedBorderTextFieldStyle())
 
+            if !connectionError.isEmpty {
+                Text(connectionError)
+                    .foregroundColor(.red)
+                    .font(.caption)
+            }
+
             HStack {
                 Button("Cancel") {
                     dismiss()
@@ -65,6 +73,8 @@ struct ServerFormView: View {
                         await testConnection()
                     }
                 }
+                .disabled(hostname.isEmpty || apiKey.isEmpty || testingConnection)
+
                 Button("Save") {
                     saveServer()
                     updateServer()
@@ -102,9 +112,21 @@ struct ServerFormView: View {
         let host = hostname.trimmingCharacters(in: .whitespacesAndNewlines)
         let key = apiKey.trimmingCharacters(in: .whitespacesAndNewlines)
 
+        await MainActor.run {
+            testingConnection = true
+            connectionError = ""
+        }
+
         let reachable = await PingService.ping(hostname: host, apiKey: key)
         await MainActor.run {
-            connectionOK = reachable
+            testingConnection = false
+            if reachable {
+                connectionOK = true
+                connectionError = ""
+            } else {
+                connectionOK = false
+                connectionError = "Connection failed. Check hostname and API key."
+            }
         }
 //
 //        guard let url = URL(string: "https://\(host)/api/v2/ping") else {