Initial implementation: host lifecycle + PXE + admin dashboard

Go service for Proxmox homelab cluster provisioning. Handles PXE boot,
Proxmox autoinstall (answer file generation), cluster join via SSH,
and Infrastructure API registration.

- Host state machine (registered → pxe_ready → installing → ready)
- dnsmasq supervisor with MAC-based allowlist
- iPXE script and Proxmox answer file generation
- First-boot phone-home → cluster join → infra registration
- Operation locking with expiry (409 on conflict)
- SSE event hub for real-time dashboard updates
- Admin dashboard (host grid, detail, registration form)
- Config-driven server types with hot-reload
- Docker deployment (multi-stage fat image)

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

internal/db/db.go

@@ -0,0 +1,81 @@
+package db
+
+import (
+	"database/sql"
+	"embed"
+	"fmt"
+	"io/fs"
+	"path/filepath"
+	"sort"
+	"strings"
+
+	_ "modernc.org/sqlite"
+)
+
+//go:embed migrations/*.sql
+var migrationsFS embed.FS
+
+func Open(path string) (*sql.DB, error) {
+	dsn := fmt.Sprintf("file:%s?_pragma=foreign_keys(1)&_pragma=journal_mode(WAL)&_pragma=busy_timeout(5000)", filepath.ToSlash(path))
+	db, err := sql.Open("sqlite", dsn)
+	if err != nil {
+		return nil, fmt.Errorf("open sqlite: %w", err)
+	}
+	if err := db.Ping(); err != nil {
+		_ = db.Close()
+		return nil, fmt.Errorf("ping sqlite: %w", err)
+	}
+	if err := migrate(db); err != nil {
+		_ = db.Close()
+		return nil, err
+	}
+	return db, nil
+}
+
+func migrate(db *sql.DB) error {
+	entries, err := fs.ReadDir(migrationsFS, "migrations")
+	if err != nil {
+		return fmt.Errorf("read migrations: %w", err)
+	}
+	names := make([]string, 0, len(entries))
+	for _, e := range entries {
+		if !e.IsDir() && strings.HasSuffix(e.Name(), ".sql") {
+			names = append(names, e.Name())
+		}
+	}
+	sort.Strings(names)
+
+	if _, err := db.Exec(`CREATE TABLE IF NOT EXISTS schema_migrations (name TEXT PRIMARY KEY, applied_at TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP)`); err != nil {
+		return fmt.Errorf("ensure schema_migrations: %w", err)
+	}
+
+	for _, name := range names {
+		var applied int
+		if err := db.QueryRow(`SELECT COUNT(1) FROM schema_migrations WHERE name = ?`, name).Scan(&applied); err != nil {
+			return fmt.Errorf("check migration %s: %w", name, err)
+		}
+		if applied > 0 {
+			continue
+		}
+		content, err := migrationsFS.ReadFile("migrations/" + name)
+		if err != nil {
+			return fmt.Errorf("read migration %s: %w", name, err)
+		}
+		tx, err := db.Begin()
+		if err != nil {
+			return fmt.Errorf("begin migration %s: %w", name, err)
+		}
+		if _, err := tx.Exec(string(content)); err != nil {
+			_ = tx.Rollback()
+			return fmt.Errorf("apply migration %s: %w", name, err)
+		}
+		if _, err := tx.Exec(`INSERT INTO schema_migrations(name) VALUES(?)`, name); err != nil {
+			_ = tx.Rollback()
+			return fmt.Errorf("record migration %s: %w", name, err)
+		}
+		if err := tx.Commit(); err != nil {
+			return fmt.Errorf("commit migration %s: %w", name, err)
+		}
+	}
+	return nil
+}