feat(feedback): implement user feedback collection system with email reporting

Backend:
- Add user_feedback table with RLS policy
- Create feedback submission API (multipart/form-data)
- Implement xlsx report generation with embedded images
- Add scheduled email delivery via Feishu SMTP
- Create HTML email templates (daily_report, no_feedback)

Frontend:
- Add feedback screen with type selection and image picker
- Support anonymous submission via skipAuth flag
- Collect device info and app version

Protocol:
- Document feedback API contract and error codes
- Update http-error-codes.md with FEEDBACK_* codes

backend/tests/integration/conftest_feedback.py

@@ -0,0 +1,43 @@
+from __future__ import annotations
+
+import os
+import time
+
+import pytest
+
+
+def pytest_configure(config):  # noqa: ARG001
+    config.addinivalue_line(
+        "markers", "integration: integration test requiring live backend"
+    )
+
+
+def pytest_collection_modifyitems(items):
+    for item in items:
+        if "integration" in item.nodeid:
+            item.add_marker(pytest.mark.integration)
+
+
+@pytest.fixture(scope="session")
+def api_base_url() -> str:
+    return os.environ.get("ERYAO_TEST_BASE_URL", "http://localhost:5775")
+
+
+@pytest.fixture
+def unique_test_email() -> str:
+    base_email = os.environ.get("ERYAO_TEST__EMAIL", "test@example.com").strip().lower()
+    if "@" in base_email:
+        name, domain = base_email.split("@", 1)
+    else:
+        name, domain = base_email, "example.com"
+    return f"{name}+fb{int(time.time() * 1000)}@{domain}"
+
+
+@pytest.fixture
+def test_verify_code() -> str:
+    return os.environ.get("ERYAO_TEST__CODE", "123456")
+
+
+@pytest.fixture
+def test_identity(unique_test_email: str, test_verify_code: str) -> dict[str, str]:
+    return {"email": unique_test_email, "code": test_verify_code}