Add Playwright e2e tests for all 8 spec acceptance scenarios

Implement browser-based e2e tests covering:
- Tests 1-5: Stats progression (cohort, feed, eggs, moves, backdating)
- Test 6: Event viewing and deletion UI
- Test 7: Harvest outcomes with yield items
- Test 8: Optimistic lock selection validation

Includes page objects for reusable form interactions and fresh_db
fixtures for tests requiring isolated database state.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

tests/e2e/pages/__init__.py

@@ -0,0 +1,16 @@
+# ABOUTME: Page object module exports for Playwright e2e tests.
+# ABOUTME: Provides clean imports for all page objects.
+
+from .animals import AnimalsPage
+from .eggs import EggsPage
+from .feed import FeedPage
+from .harvest import HarvestPage
+from .move import MovePage
+
+__all__ = [
+    "AnimalsPage",
+    "EggsPage",
+    "FeedPage",
+    "HarvestPage",
+    "MovePage",
+]