chore: name the database in every migration log line

An operator reported migrations being very slow and sent a log with three
interleaved runs — and no way to tell one database migrated three times from
three databases migrated once. Each line now carries its target: the SQLite file
name, mysql:<database>, or baseline:memory for the in-memory pass that derives
the schema for a FRESH MySQL database (that one is fast and is not a real
database — in the report it sat between two slow runs and looked like a third).

A pass also announces how many migrations it will apply, so a run that applies
nothing is visibly distinct from one that does.

internal/db/mysql.go

@@ -139,6 +139,7 @@ func translateTextColumns(s string) string {
 //     app-lifetime ctx with no per-query timeout) hold a connection for the whole
 //     chain of remote-MySQL latency, so a handful of concurrent UI bursts drained
 //     the pool and "after a while nothing updated" — grid, chat, live_status froze.
+//
 // 40 fits the actual deployment (max 5 ops on a server with max_connections=300 →
 // 40*5 = 200, leaving ~100 for phpMyAdmin/server overhead). This is the per-INSTANCE
 // pool, so keep max_connections >= pool*ops + headroom.
@@ -200,7 +201,7 @@ func OpenMySQL(c MySQLConfig) (*sql.DB, error) {
 		err = applyMySQLBaseline(conn)
 	} else {
 		// Existing database: apply only the migrations it's missing.
-		err = migrate(conn, mysqlDDL, "")
+		err = migrate(conn, mysqlDDL, "", "mysql:"+name)
 	}
 	if err != nil {
 		_ = conn.Close()
@@ -287,7 +288,11 @@ func applyMySQLBaseline(conn *sql.DB) error {
 		return fmt.Errorf("open baseline sqlite: %w", err)
 	}
 	defer mem.Close()
-	if err := migrate(mem, nil, ""); err != nil {
+	// In-memory SQLite, used only to derive the final schema for a FRESH MySQL
+	// database. Labelled so its (fast) migration lines are not mistaken for a
+	// real database being migrated — in one operator's log this pass sat between
+	// two slow MySQL runs and looked like a third database.
+	if err := migrate(mem, nil, "", "baseline:memory"); err != nil {
 		return fmt.Errorf("build baseline schema: %w", err)
 	}