Add transposed (columns-as-rows) view for query results

[jafigueroam94]

Summary

• Press T while the results table is focused to toggle a transposed view of the grid: column names run down the left side, and each original row becomes its own column - useful for wide result sets with many columns and few rows.
• Works per-section in stacked (multi-statement) results mode; each section keeps its own transpose state independently.
• Actions that assume "row = DB row, column = DB column" (edit_cell, delete_row, FK/referrers navigation, results filter, and the cell/row "Copy as..." menu) are disabled while transposed, since the cursor's row/column indices no longer map to the original data and would otherwise generate wrong SQL or mislabeled/incorrect copied output.
• Transposing is display-only: the underlying query result data is never mutated, so untransposing rebuilds the exact original grid.
• Rows beyond 200 are truncated when transposing (each original row becomes a column, and the Arrow-backed grid isn't built for hundreds of columns), with a warning notification.

No existing feature or open/closed issue/PR covered this - confirmed via a search of the repo's issues, PRs, and source before implementing.

Test plan

• uv run pytest tests/unit/test_results_transpose.py - pure transpose helper + action-level guards/behavior (fake-app harness, no Textual)
• uv run pytest tests/ui/test_results_transpose.py - end-to-end pilot tests against a real running app: toggle on/off restores the grid exactly, stacked-mode per-section toggling, focus preservation across repeated toggles, View full uses the transposed column label, new query results reset transpose state, no-results is a no-op
• uv run pytest tests/ui/keybindings/test_state_machine.py - guard/footer-binding coverage for toggle_transpose and the actions blocked while transposed
• Full suite: uv run pytest tests/ - 1855 passed, 652 skipped, only 2 pre-existing failures unrelated to this change (test_detect_strategy_pip_user_fallback, test_postgresql.py::TestPostgreSQLIntegration::test_docker_container_connection - both require infra not available in this environment)