Update Explore filter and selection interface

This PR makes a bouquet of interface changes to Explore's filtering and selection interfaces. It has companion MRs in the TorqueLLMBridge and LFCTheme repos (torquellmbridge!1 (merged) and LFCTheme!31 (merged) respectively) that should be deployed at the same time.

• Boxed in the filters
• Moved "Smart Start" to far left as suggested first item
• Moved "All filters" to the end of the filter list
• Moved "Clear filters" to the far right
• Improved the layout and typography of filter contents
• Improved wrapping behavior of long filter checkboxes (more bullet-like behavior)
• Made "Show more" / "Show less" actions more button-like
• Fixed broken "disable primary filters when All Filters sidebar is open" behavior
• Replaced old item selection menu (and paginator counter) with latest design
• Improve disabled paginator arrow design
• Converts more literal strings to i18n values

(Ignore the visible HTML in the actual results; that's a staging server issue.)

Before:

After:

Resolves https://code.librehq.com/ots/clients/lfc/torque-tracker/-/issues/200 Resolves https://code.librehq.com/ots/clients/lfc/torque-tracker/-/issues/201