Add app source and tests

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

lib/Peach/utils/Validators.dart

@@ -0,0 +1,26 @@
+// Form validators. Screens reference these rather than writing closures
+// inline, so an error message reads the same wherever the rule applies.
+
+String? requiredField(String? value) =>
+    (value == null || value.trim().isEmpty) ? 'Required' : null;
+
+String? validPort(String? value) {
+  if (value == null || value.trim().isEmpty) return null; // falls back to 22
+  final port = int.tryParse(value.trim());
+  if (port == null) return 'Numbers only';
+  if (port < 1 || port > 65535) return 'Must be 1–65535';
+  return null;
+}
+
+String? validHost(String? value) {
+  if (value == null || value.trim().isEmpty) return 'Required';
+  if (value.trim().contains(' ')) return 'No spaces allowed';
+  return null;
+}
+
+/// An absolute POSIX path, as every remote target must be.
+String? validRemotePath(String? value) {
+  if (value == null || value.trim().isEmpty) return 'Required';
+  if (!value.trim().startsWith('/')) return 'Must start with /';
+  return null;
+}