Fixed the language switcher dropdown closing before you could pick a language

The language switcher in the top nav is a hover-and-click dropdown, the same pattern the rest of the main navigation uses for its own menus (Discover, Learn, etc.). Getting it to behave exactly like those other menus took a few real attempts: an early version could require two clicks to open on a real click, and a later version could disappear entirely while you moved your mouse from the trigger toward a language option, before you had a chance to click one.

Both were caused by subtle differences between how the language switcher was built and how the rest of the nav's dropdowns work. It was not the same code, just a similar-looking copy. The fix pulls the nav's own working dropdown mechanism out into a single shared component and points both the main nav and the language switcher at it, so they can't drift apart again. As a result, the language dropdown's spacing, background, shadow, and hover colors now also match the rest of the nav exactly, instead of looking like a slightly different control.