test(e2e): add notification bell mark-as-read flow - #1018

good flow choice: driving the notification through a real mock-mode contribution instead of stubbing the feed makes this a genuine end-to-end check, and the escape-key close plus badge decrement assertions target exactly what #804 describes.

the problem is the test can silently pass without verifying anything:

1. tests/e2e/notifications.spec.ts:66-68 the mark-as-read click is wrapped in if (await markReadButton.isVisible()), and tests/e2e/notifications.spec.ts:75-77 the badge assertion is wrapped in if (initialBadgeText && initialBadgeText !== "0"). if the notification never appears, every meaningful assertion is skipped and the test goes green. make both unconditional: assert the unread badge is visible with a nonzero count after the donation, assert the mark-read button exists, then assert the decrement.
2. tests/e2e/notifications.spec.ts:53 bell.locator("span").first() is fragile; give the badge a data-testid or target it by accessible name instead.
3. tests/e2e/notifications.spec.ts:5-12 swallowing ChunkLoadError and "access control checks" page errors globally can hide real regressions; if this guard is needed it belongs in a shared fixture with a comment explaining why, not copied into one spec.
4. missing trailing newline at end of file, which is likely part of the prettier failure.

typecheck/unit/build reds look like the stale pre-#875 base, so please rebase as well.