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/test_utils.py

@@ -0,0 +1,137 @@
+"""Tests for directdnsonly.app.utils — zone index helper functions."""
+import pytest
+
+from directdnsonly.app.db.models import Domain
+from directdnsonly.app.utils import (
+    check_zone_exists,
+    check_parent_domain_owner,
+    get_domain_record,
+    get_parent_domain_record,
+    put_zone_index,
+)
+
+
+# ---------------------------------------------------------------------------
+# check_zone_exists
+# ---------------------------------------------------------------------------
+
+
+def test_check_zone_exists_not_found(patch_connect):
+    assert check_zone_exists("example.com") is False
+
+
+def test_check_zone_exists_found(patch_connect):
+    patch_connect.add(
+        Domain(domain="example.com", hostname="da1.example.com", username="admin")
+    )
+    patch_connect.commit()
+
+    assert check_zone_exists("example.com") is True
+
+
+def test_check_zone_exists_does_not_match_partial(patch_connect):
+    patch_connect.add(
+        Domain(domain="example.com", hostname="da1.example.com", username="admin")
+    )
+    patch_connect.commit()
+
+    assert check_zone_exists("sub.example.com") is False
+
+
+# ---------------------------------------------------------------------------
+# put_zone_index
+# ---------------------------------------------------------------------------
+
+
+def test_put_zone_index_adds_record(patch_connect):
+    put_zone_index("new.com", "da1.example.com", "admin")
+
+    record = patch_connect.query(Domain).filter_by(domain="new.com").first()
+    assert record is not None
+    assert record.hostname == "da1.example.com"
+    assert record.username == "admin"
+
+
+def test_put_zone_index_stores_domain_name(patch_connect):
+    put_zone_index("another.nz", "da2.example.com", "user1")
+
+    assert check_zone_exists("another.nz") is True
+
+
+# ---------------------------------------------------------------------------
+# get_domain_record
+# ---------------------------------------------------------------------------
+
+
+def test_get_domain_record_returns_none_when_missing(patch_connect):
+    assert get_domain_record("missing.com") is None
+
+
+def test_get_domain_record_returns_record(patch_connect):
+    patch_connect.add(
+        Domain(domain="found.com", hostname="da1.example.com", username="admin")
+    )
+    patch_connect.commit()
+
+    record = get_domain_record("found.com")
+    assert record is not None
+    assert record.domain == "found.com"
+    assert record.hostname == "da1.example.com"
+
+
+# ---------------------------------------------------------------------------
+# check_parent_domain_owner
+# ---------------------------------------------------------------------------
+
+
+def test_check_parent_domain_owner_not_found(patch_connect):
+    assert check_parent_domain_owner("sub.example.com") is False
+
+
+def test_check_parent_domain_owner_found(patch_connect):
+    patch_connect.add(
+        Domain(domain="example.com", hostname="da1.example.com", username="admin")
+    )
+    patch_connect.commit()
+
+    assert check_parent_domain_owner("sub.example.com") is True
+
+
+def test_check_parent_domain_owner_single_label_returns_false(patch_connect):
+    # A single-label name like "com" has no parent
+    assert check_parent_domain_owner("com") is False
+
+
+def test_check_parent_domain_owner_ignores_grandparent(patch_connect):
+    # Only the immediate parent is checked, not grandparents
+    patch_connect.add(
+        Domain(domain="example.com", hostname="da1.example.com", username="admin")
+    )
+    patch_connect.commit()
+
+    # deep.sub.example.com's immediate parent is sub.example.com (not in DB)
+    assert check_parent_domain_owner("deep.sub.example.com") is False
+
+
+# ---------------------------------------------------------------------------
+# get_parent_domain_record
+# ---------------------------------------------------------------------------
+
+
+def test_get_parent_domain_record_returns_none_when_missing(patch_connect):
+    assert get_parent_domain_record("sub.example.com") is None
+
+
+def test_get_parent_domain_record_returns_parent(patch_connect):
+    patch_connect.add(
+        Domain(domain="example.com", hostname="da1.example.com", username="admin")
+    )
+    patch_connect.commit()
+
+    parent = get_parent_domain_record("sub.example.com")
+    assert parent is not None
+    assert parent.domain == "example.com"
+
+
+def test_get_parent_domain_record_single_label_returns_none(patch_connect):
+    assert get_parent_domain_record("com") is None