docs: update CLAUDE.md with E2E test documentation

- Add E2E test command (uv run pytest tests/e2e)
- Document test_e2e schema isolation approach
- Clarify DATABASE_URL requirement for E2E tests
- Update test infrastructure descriptions

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

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

Author: MarkusNeusinger

CLAUDE.md

@@ -129,7 +129,7 @@ uv run alembic upgrade head
 ### Testing
 
 ```bash
-# Run all tests (unit + integration)
+# Run all tests (unit + integration + e2e)
 uv run pytest
 
 # Run only unit tests
@@ -138,6 +138,9 @@ uv run pytest tests/unit
 # Run only integration tests (uses SQLite in-memory)
 uv run pytest tests/integration
 
+# Run only E2E tests (requires DATABASE_URL)
+uv run pytest tests/e2e
+
 # Run with coverage
 uv run pytest --cov=. --cov-report=html
 
@@ -149,11 +152,14 @@ uv run pytest tests/unit/api/test_routers.py::test_get_specs
 ```
 
 **Test Infrastructure**:
-- **Unit tests** (`tests/unit/`): Fast, mocked dependencies, run in CI
-- **Integration tests** (`tests/integration/`): Real database operations with SQLite, run in CI
-- **E2E tests** (`tests/e2e/`): Full stack with FastAPI TestClient, not yet in CI
-
-**Database for Tests**: Integration tests use SQLite in-memory (via custom types in `core/database/types.py`). Production uses PostgreSQL native types (ARRAY, JSONB, UUID), tests use compatible fallbacks (JSON, String).
+- **Unit tests** (`tests/unit/`): Fast, mocked dependencies
+- **Integration tests** (`tests/integration/`): SQLite in-memory for API tests
+- **E2E tests** (`tests/e2e/`): Real PostgreSQL with isolated `test_e2e` schema
+
+**Database for Tests**:
+- **Unit/Integration**: SQLite in-memory (via custom types in `core/database/types.py`)
+- **E2E**: PostgreSQL with `test_e2e` schema (auto-created, auto-dropped)
+- E2E tests are skipped if `DATABASE_URL` is not set
 
 ### Code Quality