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 — 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.