feat: add gateway API, voice service, WebSocket hub, and startup entry

- services/gateway/api: net/http router with JWT auth, stub login, 6 tests
- services/gateway/ws: WebSocket hub with echo support
- services/voice: STT/TTS provider chain with fallback, 6 tests
- cmd/cyrene/main.go: single binary startup, 108 tests total
- Smoke test: health check + login verified on :8080

backend/internal/db/db.go

@@ -6,6 +6,7 @@ import (
 	"database/sql"
 	"fmt"
 	"log"
+	"strings"
 	"time"
 
 	_ "github.com/lib/pq" // PostgreSQL driver
@@ -117,7 +118,6 @@ func Transaction(ctx context.Context, db *sql.DB, fn func(tx *sql.Tx) error) err
 }
 
 // RunMigration executes a list of SQL migration statements in order.
-// Each migration is run within its own transaction.
 func RunMigration(ctx context.Context, db *sql.DB, name string, statements []string) error {
 	log.Printf("[db] running migration: %s (%d statements)", name, len(statements))
 
@@ -129,3 +129,16 @@ func RunMigration(ctx context.Context, db *sql.DB, name string, statements []str
 	log.Printf("[db] migration %s completed", name)
 	return nil
 }
+
+// SplitSQL splits a multi-statement SQL string on semicolons.
+func SplitSQL(sql string) []string {
+	parts := strings.Split(sql, ";")
+	result := make([]string, 0, len(parts))
+	for _, p := range parts {
+		p = strings.TrimSpace(p)
+		if p != "" && !strings.HasPrefix(p, "--") {
+			result = append(result, p)
+		}
+	}
+	return result
+}