fix(DIDView): validate DID format before processing URL parameters

- Add DID validation using isDid() function to prevent invalid DIDs from loading current user's info
- Show error message and redirect to HomeView for invalid DID formats (e.g., /did/0)
- Import NOTIFY_CONTACT_INVALID_DID constant for consistent error messaging

Resolves: DIDView loading current user's info for invalid DID parameters

test-playwright/00-noid-tests.spec.ts

@@ -70,6 +70,7 @@
 
 import { test, expect } from '@playwright/test';
 import { deleteContact, generateAndRegisterEthrUser, importUser } from './testUtils';
+import { NOTIFY_CONTACT_INVALID_DID } from '../src/constants/notifications';
 
 test('Check activity feed - check that server is running', async ({ page }) => {
   // Load app homepage
@@ -169,6 +170,19 @@ test('Confirm test API setting (may fail if you are running your own Time Safari
   await expect(page.locator('#apiServerInput')).toHaveValue(endorserServer);
 });
 
+test('Check invalid DID shows error and redirects', async ({ page }) => {
+  await importUser(page, '00');
+  
+  // Navigate to an invalid DID URL
+  await page.goto('./did/0');
+  
+  // Should show error message about invalid DID format
+  await expect(page.getByText(NOTIFY_CONTACT_INVALID_DID.message)).toBeVisible();
+  
+  // Should redirect to contacts page
+  await expect(page).toHaveURL(/.*\/contacts$/);
+});
+
 test('Check User 0 can register a random person', async ({ page }) => {
   await importUser(page, '00');
   const newDid = await generateAndRegisterEthrUser(page);