feat(data-grid): add SQL INSERT as a copy format option

[thomaswasle]

Adds SQL INSERT as a third option in the copy format selector, alongside the existing CSV and JSON options. Once selected,
Ctrl+C and right-click → "Copy selected row(s)" both produce ready-to-paste INSERT statements.

Example output:
INSERT INTO users (id, name, email) VALUES (1, 'Alice', 'alice@example.com');
INSERT INTO users (id, name, email) VALUES (2, NULL, 'bob@example.com');

Value quoting: null → NULL, booleans → TRUE/FALSE, numbers unquoted, strings/objects single-quoted with '' escaping.

Changes

• CopyFormat type (SettingsContext.ts) extended to "csv" | "json" | "sql-insert" — all downstream prop types updated
  (DataGrid, MultiResultPanel, StackedResultItem, ResultEntryContent, Editor)
• clipboard.ts — adds rowsToSqlInsert (and private helper rowToSqlInsert, sqlValue)
• DataGrid.formatRows — routes "sql-insert" through rowsToSqlInsert; falls back to "table" as the identifier when no
  tableName prop is present (plain query results)
• Settings panel (GeneralTab.tsx) and editor toolbar (Editor.tsx) both expose the new option