add database migration and UserRepository wrapper

- implemented DB migration

- added UserRepository for DB interactions

- inserted initial test record

migrations/001_init.sql

@@ -0,0 +1,30 @@
+CREATE TABLE IF NOT EXISTS users (
+    id INTEGER PRIMARY KEY AUTOINCREMENT,
+    email TEXT NOT NULL,
+    password_hash TEXT NOT NULL,
+    is_active INTEGER NOT NULL DEFAULT 1,
+    created_at TEXT NOT NULL,
+    updated_at TEXT NOT NULL
+);
+
+CREATE UNIQUE INDEX IF NOT EXISTS idx_users_email
+ON users(email);
+
+CREATE TABLE IF NOT EXISTS sessions (
+    id INTEGER PRIMARY KEY AUTOINCREMENT,
+    user_id INTEGER NOT NULL,
+    token_hash TEXT NOT NULL,
+    created_at TEXT NOT NULL,
+    expires_at TEXT NOT NULL,
+    revoked_at TEXT,
+    FOREIGN KEY(user_id) REFERENCES users(id)
+);
+
+CREATE UNIQUE INDEX IF NOT EXISTS idx_sessions_token_hash
+ON sessions(token_hash);
+
+CREATE INDEX IF NOT EXISTS idx_sessions_user_id
+ON sessions(user_id);
+
+CREATE INDEX IF NOT EXISTS idx_sessions_expires_at
+ON sessions(expires_at);