fix: convert MySQL logbook to utf8mb4 (fixes 1366 on Cyrillic/Polish)

A QSO with a non-Latin character (Cyrillic Я = \xD0\xAF, Polish ł, …) failed to
save on the shared MySQL backend with "Error 1366: Incorrect string value …
for column 'qso'.'address'". Cause: the database had been pre-created by a
hosting panel (o2switch/cPanel) as latin1, so OpsLog's CREATE DATABASE IF NOT
EXISTS … utf8mb4 was a no-op and every table inherited latin1 — which can't
store those letters, even over a utf8mb4 connection.

OpenMySQL now runs ensureMySQLUTF8MB4 after migrations: ALTER DATABASE to
utf8mb4 (for future tables) + CONVERT any table with a non-utf8mb4 text column
via an information_schema probe. Idempotent and cheap on a healthy DB (the probe
returns nothing → no ALTERs); best-effort so a charset issue never blocks
logbook access. SQLite is unaffected.

internal/db/mysql.go

@@ -207,9 +207,58 @@ func OpenMySQL(c MySQLConfig) (*sql.DB, error) {
 		Dialect = "sqlite" // migration failed; we'll fall back to SQLite
 		return nil, err
 	}
+	// Guarantee the schema can store non-Latin text (Cyrillic, Polish ł, …).
+	// Best-effort: never block access to the logbook over the charset probe.
+	if err := ensureMySQLUTF8MB4(conn, name); err != nil {
+		fmt.Printf("OpsLog: utf8mb4 conversion: %v\n", err)
+	}
 	return conn, nil
 }
 
+// ensureMySQLUTF8MB4 makes the database default and every OpsLog table utf8mb4,
+// converting any that isn't. It repairs databases pre-created as latin1 or
+// utf8mb3 by a hosting panel (cPanel/o2switch default), where OpsLog's
+// "CREATE DATABASE IF NOT EXISTS … utf8mb4" was a no-op and the tables inherited
+// a charset that can't store non-Latin callsigns/names/QTHs — the MySQL 1366
+// "Incorrect string value: '\xD0\xAF'" (Cyrillic Я) seen updating a QSO from QRZ.
+//
+// Idempotent and cheap on a healthy database: one information_schema probe finds
+// the tables with a non-utf8mb4 text column, and only those are converted (none
+// on an already-correct DB). Conversion is safe for the wide qso table because
+// the bulk of its columns are off-page TEXT (see the row-size note above); only
+// the ~20 indexed VARCHARs sit in-row, well under InnoDB's 65535-byte limit even
+// at 4 bytes/char.
+func ensureMySQLUTF8MB4(conn *sql.DB, dbName string) error {
+	// Fix the database default so any FUTURE table is utf8mb4 too.
+	_, _ = conn.Exec("ALTER DATABASE `" + dbName + "` CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci")
+
+	rows, err := conn.Query(`
+		SELECT DISTINCT TABLE_NAME
+		FROM information_schema.COLUMNS
+		WHERE TABLE_SCHEMA = ?
+		  AND CHARACTER_SET_NAME IS NOT NULL
+		  AND CHARACTER_SET_NAME <> 'utf8mb4'`, dbName)
+	if err != nil {
+		return fmt.Errorf("probe charsets: %w", err)
+	}
+	var tables []string
+	for rows.Next() {
+		var t string
+		if err := rows.Scan(&t); err == nil && validDBIdent(t) {
+			tables = append(tables, t)
+		}
+	}
+	rows.Close()
+
+	var firstErr error
+	for _, t := range tables {
+		if _, err := conn.Exec("ALTER TABLE `" + t + "` CONVERT TO CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci"); err != nil && firstErr == nil {
+			firstErr = fmt.Errorf("convert %s: %w", t, err)
+		}
+	}
+	return firstErr
+}
+
 // isFreshMySQL reports whether the database has no OpsLog schema yet (no qso
 // table), so the baseline fast-path applies. A partially-migrated database is
 // NOT fresh and goes through the incremental migrator.