feat: init pc-monitor project

- Client: Go-based Windows hardware monitoring (CPU, GPU, memory, disk, network, power)
- Server: Go + Gin + SQLite backend with REST API
- Frontend: Vue 3 + Element Plus dashboard
- Docker deployment support
- Windows service installation script

server/repository/db.go

@@ -0,0 +1,94 @@
+package repository
+
+import (
+	"database/sql"
+	"os"
+	"path/filepath"
+
+	_ "github.com/mattn/go-sqlite3"
+)
+
+func NewDB(dbPath string) (*sql.DB, error) {
+	dir := filepath.Dir(dbPath)
+	if err := os.MkdirAll(dir, 0755); err != nil {
+		return nil, err
+	}
+
+	db, err := sql.Open("sqlite3", dbPath+"?_journal_mode=WAL")
+	if err != nil {
+		return nil, err
+	}
+
+	if err := initSchema(db); err != nil {
+		db.Close()
+		return nil, err
+	}
+
+	return db, nil
+}
+
+func initSchema(db *sql.DB) error {
+	schema := `
+	CREATE TABLE IF NOT EXISTS devices (
+		id TEXT PRIMARY KEY,
+		hostname TEXT NOT NULL,
+		os TEXT NOT NULL,
+		ip TEXT NOT NULL,
+		registered_at DATETIME NOT NULL,
+		last_report_at DATETIME NOT NULL,
+		status TEXT NOT NULL DEFAULT 'offline'
+	);
+
+	CREATE TABLE IF NOT EXISTS metrics (
+		id INTEGER PRIMARY KEY AUTOINCREMENT,
+		device_id TEXT NOT NULL,
+		timestamp DATETIME NOT NULL,
+		cpu_usage REAL,
+		cpu_temperature REAL,
+		cpu_core_usage TEXT,
+		memory_total INTEGER,
+		memory_used INTEGER,
+		memory_usage REAL,
+		gpu_usage REAL,
+		gpu_temperature REAL,
+		gpu_memory_total INTEGER,
+		gpu_memory_used INTEGER,
+		gpu_name TEXT,
+		network_interfaces TEXT,
+		disks TEXT,
+		power_status TEXT,
+		battery_level INTEGER,
+		power_source TEXT,
+		FOREIGN KEY (device_id) REFERENCES devices(id)
+	);
+
+	CREATE INDEX IF NOT EXISTS idx_metrics_device_time ON metrics(device_id, timestamp);
+
+	CREATE TABLE IF NOT EXISTS alert_rules (
+		id TEXT PRIMARY KEY,
+		device_id TEXT NOT NULL,
+		metric TEXT NOT NULL,
+		operator TEXT NOT NULL,
+		threshold REAL NOT NULL,
+		duration INTEGER NOT NULL DEFAULT 0,
+		created_at DATETIME NOT NULL,
+		FOREIGN KEY (device_id) REFERENCES devices(id)
+	);
+
+	CREATE TABLE IF NOT EXISTS alerts (
+		id TEXT PRIMARY KEY,
+		device_id TEXT NOT NULL,
+		rule_id TEXT NOT NULL,
+		metric TEXT NOT NULL,
+		value REAL NOT NULL,
+		message TEXT NOT NULL,
+		status TEXT NOT NULL DEFAULT 'active',
+		created_at DATETIME NOT NULL,
+		resolved_at DATETIME,
+		FOREIGN KEY (device_id) REFERENCES devices(id),
+		FOREIGN KEY (rule_id) REFERENCES alert_rules(id)
+	);
+	`
+	_, err := db.Exec(schema)
+	return err
+}