Add context information to Debug::dump()

[giuscris]

This pull request enhances the debug output in the Debug class to provide better context and improve readability. The changes ensure that debug dumps are only shown when HTML output is appropriate, add context about where the dump was called, and improve the visual separation of dumped items.

Debug output improvements:

• The dump method now only outputs debug information if the client accepts HTML, preventing unwanted output in non-HTML contexts.
• Each debug dump now includes contextual information (file name and line number) about where the dump was called, using the new getContext() method and a backtrace limit. [1] [2] [3]
• Dumped items are visually separated with a dashed border and spacing for better readability, thanks to new CSS rules.
• Each dumped value is wrapped in its own container, making the output clearer and easier to scan.