Increase e2e test timeouts on CI to fix flaky tests (#37053)

Introduce a `GITEA_TEST_E2E_TIMEOUT_FACTOR` env var (3 on CI, 1 locally,
overridable) to scale Playwright e2e timeouts, fixing flaky tests like
`logout propagation` that timed out waiting for SSE event propagation on
slow CI runners.

| Timeout | Before (local) | After (local) | Before (CI) | After (CI) |
|---|---|---|---|---|
| expect | 3000 | 5000 | 6000 | 15000 |
| action | 3000 | 5000 | 6000 | 15000 |
| test | 6000 | 10000 | 12000 | 30000 |
| navigation | 6000 | 10000 | 12000 | 30000 |

---
This PR was written with the help of Claude Opus 4.6

---------

Co-authored-by: Claude (Opus 4.6) <noreply@anthropic.com>

playwright.config.ts

@@ -1,5 +1,7 @@
 import {env} from 'node:process';
 import {defineConfig, devices} from '@playwright/test';
+const timeoutFactor = Number(env.GITEA_TEST_E2E_TIMEOUT_FACTOR) || 1;
+const timeout = 5000 * timeoutFactor;
 
 export default defineConfig({
   testDir: './tests/e2e/',
@@ -7,15 +9,15 @@ export default defineConfig({
   testMatch: /.*\.test\.ts/,
   forbidOnly: Boolean(env.CI),
   reporter: 'list',
-  timeout: env.CI ? 12000 : 6000,
+  timeout: 2 * timeout,
   expect: {
-    timeout: env.CI ? 6000 : 3000,
+    timeout,
   },
   use: {
     baseURL: env.GITEA_TEST_E2E_URL?.replace?.(/\/$/g, ''),
     locale: 'en-US',
-    actionTimeout: env.CI ? 6000 : 3000,
-    navigationTimeout: env.CI ? 12000 : 6000,
+    actionTimeout: timeout,
+    navigationTimeout: 2 * timeout,
   },
   projects: [
     {