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/feed.py

@@ -0,0 +1,100 @@
+# ABOUTME: Page object for feed management pages (purchase, give feed).
+# ABOUTME: Encapsulates navigation and form interactions for feed operations.
+
+from playwright.sync_api import Page, expect
+
+
+class FeedPage:
+    """Page object for feed management pages."""
+
+    def __init__(self, page: Page, base_url: str):
+        self.page = page
+        self.base_url = base_url
+
+    def goto_feed_page(self):
+        """Navigate to the feed quick capture page."""
+        self.page.goto(f"{self.base_url}/feed")
+        expect(self.page.locator("body")).to_be_visible()
+
+    def purchase_feed(
+        self,
+        *,
+        feed_type: str = "layer",
+        bag_size_kg: int,
+        bags_count: int,
+        bag_price_euros: float,
+        vendor: str = "",
+        notes: str = "",
+    ):
+        """Fill and submit the feed purchase form.
+
+        Args:
+            feed_type: Feed type code (e.g., "layer")
+            bag_size_kg: Size of each bag in kg
+            bags_count: Number of bags
+            bag_price_euros: Price per bag in EUR
+            vendor: Optional vendor name
+            notes: Optional notes
+        """
+        self.goto_feed_page()
+
+        # The purchase form uses specific IDs
+        self.page.select_option("#purchase_feed_type_code", feed_type)
+        self.page.fill("#bag_size_kg", str(bag_size_kg))
+        self.page.fill("#bags_count", str(bags_count))
+        self.page.fill("#bag_price_euros", str(bag_price_euros))
+
+        if vendor:
+            self.page.fill("#vendor", vendor)
+
+        if notes:
+            self.page.fill("#purchase_notes", notes)
+
+        # Submit the purchase form (second form on page)
+        self.page.click('form[hx-post*="feed-purchased"] button[type="submit"]')
+
+        # Wait for HTMX response
+        self.page.wait_for_load_state("networkidle")
+
+    def give_feed(
+        self,
+        *,
+        location_name: str,
+        feed_type: str = "layer",
+        amount_kg: int,
+        notes: str = "",
+    ):
+        """Fill and submit the feed given form.
+
+        Args:
+            location_name: Human-readable location name (e.g., "Strip 1")
+            feed_type: Feed type code (e.g., "layer")
+            amount_kg: Amount of feed in kg
+            notes: Optional notes
+        """
+        self.goto_feed_page()
+
+        # The give form uses specific IDs
+        self.page.select_option("#location_id", label=location_name)
+        self.page.select_option("#feed_type_code", feed_type)
+        self.page.fill("#amount_kg", str(amount_kg))
+
+        if notes:
+            self.page.fill("#notes", notes)
+
+        # Submit the give form (first form on page)
+        self.page.click('form[hx-post*="feed-given"] button[type="submit"]')
+
+        # Wait for HTMX response
+        self.page.wait_for_load_state("networkidle")
+
+    def get_feed_inventory_balance(self, feed_type: str = "layer") -> dict:
+        """Get the current feed inventory from the page stats.
+
+        Returns dict with purchased_kg, given_kg, balance_kg if visible,
+        or empty dict if stats not found.
+        """
+        # This depends on how stats are displayed on the page
+        # May need to parse text content from stats section
+        # For now, return empty - can be enhanced based on actual UI
+        return {}