refactor: migrate data storage from JSON/map files to SQLite

Replace servers.json, certificates.json, and map file parsing with
SQLite (WAL mode) as single source of truth. HAProxy map files are
now generated from SQLite via sync_map_files().

Key changes:
- Add db.py with schema, connection management, and JSON migration
- Add DB_FILE config constant
- Delegate file_ops.py functions to db.py
- Refactor domains.py to use file_ops instead of direct list manipulation
- Fix subprocess.TimeoutExpired not caught (doesn't inherit TimeoutError)
- Add DB health check in health.py
- Init DB on startup in server.py and __main__.py
- Update all 359 tests to use SQLite-backed functions

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

tests/conftest.py

@@ -255,6 +255,8 @@ def temp_config_dir(tmp_path):
     state_file = tmp_path / "servers.state"
     state_file.write_text("")
 
+    db_file = tmp_path / "haproxy_mcp.db"
+
     return {
         "dir": tmp_path,
         "map_file": str(map_file),
@@ -262,12 +264,15 @@ def temp_config_dir(tmp_path):
         "servers_file": str(servers_file),
         "certs_file": str(certs_file),
         "state_file": str(state_file),
+        "db_file": str(db_file),
     }
 
 
 @pytest.fixture
 def patch_config_paths(temp_config_dir):
     """Fixture that patches config module paths to use temporary directory."""
+    from haproxy_mcp.db import close_connection, init_db
+
     with patch.multiple(
         "haproxy_mcp.config",
         MAP_FILE=temp_config_dir["map_file"],
@@ -275,16 +280,34 @@ def patch_config_paths(temp_config_dir):
         SERVERS_FILE=temp_config_dir["servers_file"],
         CERTS_FILE=temp_config_dir["certs_file"],
         STATE_FILE=temp_config_dir["state_file"],
+        DB_FILE=temp_config_dir["db_file"],
     ):
         # Also patch file_ops module which imports these
         with patch.multiple(
             "haproxy_mcp.file_ops",
             MAP_FILE=temp_config_dir["map_file"],
             WILDCARDS_MAP_FILE=temp_config_dir["wildcards_file"],
-            SERVERS_FILE=temp_config_dir["servers_file"],
-            CERTS_FILE=temp_config_dir["certs_file"],
         ):
-            yield temp_config_dir
+            # Patch db module which imports these
+            with patch.multiple(
+                "haproxy_mcp.db",
+                MAP_FILE=temp_config_dir["map_file"],
+                WILDCARDS_MAP_FILE=temp_config_dir["wildcards_file"],
+                SERVERS_FILE=temp_config_dir["servers_file"],
+                CERTS_FILE=temp_config_dir["certs_file"],
+                DB_FILE=temp_config_dir["db_file"],
+            ):
+                # Patch health module which imports MAP_FILE and DB_FILE
+                with patch.multiple(
+                    "haproxy_mcp.tools.health",
+                    MAP_FILE=temp_config_dir["map_file"],
+                    DB_FILE=temp_config_dir["db_file"],
+                ):
+                    # Close any existing connection and initialize fresh DB
+                    close_connection()
+                    init_db()
+                    yield temp_config_dir
+                    close_connection()
 
 
 @pytest.fixture