feat: initial project setup with implementation plan

- Add PLAN.md with 40-step checklist across 10 phases
- Add CLAUDE.md with project-specific instructions
- Set up nix flake with FastHTML/MonsterUI dependencies
- Create Python package skeleton (src/animaltrack)
- Vendor FastHTML and MonsterUI documentation
- Add Docker build configuration

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

tests/__init__.py

@@ -0,0 +1,2 @@
+# ABOUTME: Test package for AnimalTrack.
+# ABOUTME: Contains unit, integration, and E2E tests.

tests/conftest.py

@@ -0,0 +1,22 @@
+# ABOUTME: Pytest configuration and fixtures for AnimalTrack tests.
+# ABOUTME: Provides database fixtures, test clients, and common utilities.
+
+import pytest
+import tempfile
+import os
+
+
+@pytest.fixture
+def temp_db_path():
+    """Create a temporary database file path for testing."""
+    with tempfile.NamedTemporaryFile(suffix=".db", delete=False) as f:
+        db_path = f.name
+    yield db_path
+    # Cleanup
+    if os.path.exists(db_path):
+        os.unlink(db_path)
+    # Also clean up WAL files if they exist
+    for suffix in ["-shm", "-wal", "-journal"]:
+        wal_path = db_path + suffix
+        if os.path.exists(wal_path):
+            os.unlink(wal_path)