fix: Improve `Tab`display

[ndonkoHenri]

Fix #5599

Summary by Sourcery

Improve tab rendering and per-control theming by centralizing control context handling and aligning Tabs with Flutter's Tab heuristics.

New Features:

• Add a reusable control context wrapper that combines control reactivity and per-control theming for all controls.
• Expose a Control extension method to build widgets within the standardized control context.

Bug Fixes:

• Fix inconsistent Tab display by ensuring TabBar sees tab widgets as Tab instances and by aligning icon/text hints and sizing behavior.

Enhancements:

• Refactor ControlWidget to use the new control context helper, simplifying widget construction and theme application.
• Introduce a TabControl that extends Flutter's Tab to provide better integration with TabBar sizing and icon/label heuristics while still using Flet controls for content.
• Ensure TabBar tabs created from arbitrary controls are wrapped in Tab widgets for consistent hover and splash behavior.
• Add per-control theme resolution that respects theme, dark_theme, and theme_mode properties, falling back to the parent theme and system brightness as appropriate.