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_zone_parser.py

@@ -0,0 +1,100 @@
+"""Tests for directdnsonly.app.utils.zone_parser."""
+import pytest
+from dns.exception import DNSException
+
+from directdnsonly.app.utils.zone_parser import (
+    count_zone_records,
+    validate_and_normalize_zone,
+)
+
+# ---------------------------------------------------------------------------
+# Helpers
+# ---------------------------------------------------------------------------
+
+MINIMAL_ZONE = "example.com. 300 IN A 1.2.3.4"
+
+FULL_ZONE = """\
+$ORIGIN example.com.
+$TTL 300
+@ IN SOA ns1.example.com. admin.example.com. 2024010101 3600 900 604800 300
+@ IN NS ns1.example.com.
+@ IN A 1.2.3.4
+www IN A 5.6.7.8
+mail IN MX 10 mail.example.com.
+"""
+
+
+# ---------------------------------------------------------------------------
+# validate_and_normalize_zone
+# ---------------------------------------------------------------------------
+
+
+def test_validate_adds_origin_when_missing():
+    result = validate_and_normalize_zone(MINIMAL_ZONE, "example.com")
+    assert "$ORIGIN example.com." in result
+
+
+def test_validate_adds_ttl_when_missing():
+    result = validate_and_normalize_zone(MINIMAL_ZONE, "example.com")
+    assert "$TTL" in result
+
+
+def test_validate_does_not_duplicate_origin():
+    zone = "$ORIGIN example.com.\nexample.com. 300 IN A 1.2.3.4"
+    result = validate_and_normalize_zone(zone, "example.com")
+    assert result.count("$ORIGIN") == 1
+
+
+def test_validate_does_not_duplicate_ttl():
+    zone = "$TTL 300\nexample.com. 300 IN A 1.2.3.4"
+    result = validate_and_normalize_zone(zone, "example.com")
+    assert result.count("$TTL") == 1
+
+
+def test_validate_appends_dot_to_domain():
+    result = validate_and_normalize_zone(MINIMAL_ZONE, "example.com")
+    assert "$ORIGIN example.com." in result
+
+
+def test_validate_returns_string():
+    result = validate_and_normalize_zone(MINIMAL_ZONE, "example.com")
+    assert isinstance(result, str)
+
+
+def test_validate_full_zone_passes():
+    result = validate_and_normalize_zone(FULL_ZONE, "example.com")
+    assert result is not None
+
+
+def test_validate_raises_on_invalid_zone():
+    bad_zone = "this is not a zone file at all !!!"
+    with pytest.raises(ValueError, match="Invalid zone data"):
+        validate_and_normalize_zone(bad_zone, "example.com")
+
+
+# ---------------------------------------------------------------------------
+# count_zone_records
+# ---------------------------------------------------------------------------
+
+
+def test_count_records_simple_zone():
+    zone = "$ORIGIN example.com.\n$TTL 300\n@ IN A 1.2.3.4\n@ IN AAAA ::1\n"
+    count = count_zone_records(zone, "example.com")
+    assert count == 2
+
+
+def test_count_records_soa_included():
+    count = count_zone_records(FULL_ZONE, "example.com")
+    # SOA + NS + A (apex) + A (www) + MX = 5
+    assert count == 5
+
+
+def test_count_records_returns_negative_on_bad_zone():
+    count = count_zone_records("not a valid zone", "example.com")
+    assert count == -1
+
+
+def test_count_records_empty_zone():
+    zone = "$ORIGIN example.com.\n$TTL 300\n"
+    count = count_zone_records(zone, "example.com")
+    assert count == 0