feat: allow creating external repositories directly from git mount editor

- Add createExternalRepository API function
- Update GitMountEditor with "+ Add new repository..." option
- Show form to enter repo name and remote URL
- Auto-create external repo and refresh list on success
- Update config-profiles page to pass onCreateRepository handler

apps/web/src/styles.css

@@ -4131,3 +4131,28 @@ a.nav-item,
   margin-top: 0.5rem;
 }
 
+.new-repo-form {
+  display: flex;
+  flex-direction: column;
+  gap: 0.5rem;
+  padding: 0.75rem;
+  background: var(--bg);
+  border: 1px solid var(--border);
+  border-radius: 0.375rem;
+}
+
+.new-repo-form input {
+  padding: 0.5rem;
+  border: 1px solid var(--border);
+  border-radius: 0.375rem;
+  background: var(--surface);
+  color: var(--text);
+  font-size: 0.875rem;
+}
+
+.new-repo-actions {
+  display: flex;
+  gap: 0.5rem;
+  margin-top: 0.25rem;
+}
+