feat: add test suite, fix backend bugs, remove legacy artifacts 🧪

- Add 73-test suite across conftest, utils, admin API, reconciler, zone parser,
  and CoreDNS MySQL backend (all green, ~0.5s)
- Fix zone_exists filter using wrong column name (name → zone_name)
- Fix delete_zone missing dot_fqdn normalization on lookup
- Remove spurious unused `from config import config` in coredns_mysql.py
- Fix config loader to search module-relative path so tests find app.yml
  without needing a root-level config/ directory
- Remove legacy v1 Flask prototype (app.py), empty config.json, and
  duplicate root config/app.yml

tests/conftest.py

@@ -0,0 +1,36 @@
+"""Shared test fixtures for directdnsonly test suite."""
+import pytest
+from sqlalchemy import create_engine
+from sqlalchemy.orm import sessionmaker
+
+from directdnsonly.app.db import Base
+from directdnsonly.app.db.models import Domain, Key  # noqa: F401 — registers models with Base
+
+
+@pytest.fixture
+def engine():
+    eng = create_engine("sqlite:///:memory:")
+    Base.metadata.create_all(eng)
+    yield eng
+    eng.dispose()
+
+
+@pytest.fixture
+def db_session(engine):
+    session = sessionmaker(bind=engine)()
+    yield session
+    session.close()
+
+
+@pytest.fixture
+def patch_connect(db_session, monkeypatch):
+    """Patch connect() at every call-site, returning the shared test session.
+
+    Modules that import connect() directly (e.g. utils, reconciler) are
+    patched at their local name so the in-memory SQLite session is used
+    instead of trying to read from vyper config.
+    """
+    _factory = lambda: db_session  # noqa: E731
+    monkeypatch.setattr("directdnsonly.app.utils.connect", _factory)
+    monkeypatch.setattr("directdnsonly.app.reconciler.connect", _factory)
+    return db_session