ui(mysql): horizontal scroll for table toolbar under narrow width

[ZhuchkaTriplesix]

Parent

Part of #445

Severity

Medium

Problem

MySQL table toolbar is a fixed-height Row of actions/pager with no horizontal scroll. Postgres/extension toolbars already use SingleChildScrollView + layout overflow tests. Narrow split / high text scale → RenderFlex overflow.

Evidence

• lib/features/mysql/mysql_table_view.dart toolbar (~422–497)
• Good pattern: Postgres table toolbar + postgres_table_toolbar_layout_test.dart

Acceptance

• Narrow viewport does not overflow (layout overflow harness)
• All toolbar actions remain reachable via horizontal scroll
• Layout test parity with Postgres toolbar

Suggested fix

Reuse Postgres/extension scrollable toolbar pattern (or extract shared strip).

[ZhuchkaTriplesix]

Shipped on dev via #461 (Closes did not auto-close because PRs targeted dev).