fix: ConfigTemplate infinite re-render loop and add E2E test

e2e/environment.spec.ts

@@ -105,4 +105,55 @@ test.describe('Environment Management', () => {
     await page.waitForTimeout(200);
     await expect(page.locator('#environments')).toBeVisible();
   });
+
+  test('should add params and edit template manually', async ({ page }) => {
+    await page.goto('/');
+    await page.click('button:has-text("Create new")');
+
+    // Step 1: Add a param to DEFAULT
+    const nameInput = page.locator('input[placeholder="name"]').first();
+    const valueInput = page.locator('input[placeholder="value"]').first();
+    const addButton = page.locator('button.btn-success').first();
+    
+    await nameInput.fill('host');
+    await valueInput.fill('localhost:8080');
+    await addButton.click();
+    await page.waitForTimeout(500);
+
+    // Add second param
+    await nameInput.fill('port');
+    await valueInput.fill('9090');
+    await addButton.click();
+    await page.waitForTimeout(500);
+
+    // Step 2: Switch to Content Template tab
+    await page.click('a:has-text("Content Template")');
+    await page.waitForTimeout(500);
+
+    // Verify the tab content is visible (check for Edit button)
+    await expect(page.locator('button:has-text("Edit")')).toBeVisible();
+
+    // Step 3: Click Edit button
+    await page.click('button:has-text("Edit")');
+    await page.waitForTimeout(500);
+
+    // Step 4: Verify textarea is visible
+    const textarea = page.locator('textarea');
+    await expect(textarea).toBeVisible();
+    
+    // Step 5: Edit the template manually - add a new key
+    await textarea.fill('{\n    "!!! host": "@host@",\n    "!!! port": "@port@",\n    "!!! custom": "@custom@"\n}');
+    await page.waitForTimeout(300);
+
+    // Step 6: Click Save
+    await page.click('button:has-text("Save")');
+    await page.waitForTimeout(500);
+
+    // Step 7: Verify the template was saved (Edit button should be visible again)
+    await expect(page.locator('button:has-text("Edit")')).toBeVisible();
+    
+    // Verify the content contains the new key
+    const pageContent = await page.content();
+    expect(pageContent).toContain('!!! custom');
+  });
 });