fix: replace hardcoded test passwords with runtime-generated UUIDs

Generate random passwords in global-setup and share via temp file so
all Playwright workers use the same credentials. Screenshot scripts
use module-level crypto.randomUUID() since they run single-process.
Unit test auth passwords also use randomUUID().

Eliminates security scanner alerts for passwords committed to git.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

tests/e2e/global-setup.ts

@@ -1,6 +1,8 @@
-import { existsSync, unlinkSync } from 'fs';
+import { existsSync, unlinkSync, writeFileSync } from 'fs';
+import { randomUUID } from 'crypto';
 
 const TEST_DB = './data/test-crumbs.db';
+export const TEST_CREDENTIALS_FILE = './data/test-credentials.json';
 
 export default function globalSetup() {
 	// Clean test database before E2E run so each run starts fresh
@@ -10,4 +12,14 @@ export default function globalSetup() {
 			unlinkSync(path);
 		}
 	}
+
+	// Generate random passwords for this test run, shared across all workers
+	writeFileSync(
+		TEST_CREDENTIALS_FILE,
+		JSON.stringify({
+			testPassword: `test-${randomUUID()}`,
+			collabPassword: `collab-${randomUUID()}`,
+			userPassword: `user-${randomUUID()}`
+		})
+	);
 }