Fix textual-fastdatatable 0.19 rendering compatibility

[Maxteabag]

Summary

• accept the new optional max_width argument passed by textual-fastdatatable 0.19
• pin textual-fastdatatable exactly to 0.19.0 so untested releases cannot silently break fresh installations
• refresh the lockfile for the pinned dependency and its Textual requirement
• add a regression that exercises both the overridden hook and a mounted table render

Root cause

sqlit-tui previously allowed textual-fastdatatable>=0.14.0. Version 0.19.0 added a max_width keyword to _get_cell_renderable(), but SqlitDataTable still overrode the earlier two-argument signature. Fresh installs or dependency upgrades resolving 0.19 therefore raised TypeError while rendering result cells.

Because sqlit integrates with a protected FastDataTable hook and the dependency is still pre-1.0, upgrades are now explicit and test-gated instead of floating automatically.

Fixes #301.

Validation

• focused compatibility/blob tests: 4 passed
• full UI suite: 302 passed
• exact 0.19.0 environment verified
• Ruff and structured autoreview: clean