refactor(jarca-ledger): implement BAT-010 backend core layering

jarca_ledger_mcp/infrastructure/sqlite/connection.py

@@ -0,0 +1,39 @@
+from __future__ import annotations
+
+import os
+import sqlite3
+from contextlib import contextmanager
+from pathlib import Path
+from typing import Iterator
+
+DEFAULT_DB_PATH = Path.home() / ".local" / "share" / "jarca" / "ledger.sqlite3"
+
+
+def resolve_db_path(db_path: str | None = None) -> Path:
+    raw = db_path or os.getenv("JARCA_LEDGER_DB_PATH") or str(DEFAULT_DB_PATH)
+    return Path(raw).expanduser().resolve()
+
+
+def connect(db_path: str | None = None) -> sqlite3.Connection:
+    path = resolve_db_path(db_path)
+    path.parent.mkdir(parents=True, exist_ok=True)
+    conn = sqlite3.connect(path)
+    conn.row_factory = sqlite3.Row
+    conn.execute("PRAGMA foreign_keys=ON")
+    return conn
+
+
+@contextmanager
+def db(db_path: str | None = None) -> Iterator[sqlite3.Connection]:
+    from .migrations import init_db
+
+    init_db(db_path)
+    conn = connect(db_path)
+    try:
+        yield conn
+        conn.commit()
+    except Exception:
+        conn.rollback()
+        raise
+    finally:
+        conn.close()