Fix search expanded state pushing SSE badge out of viewport

Commit notes

- Add min-w-0 to header flex container to allow proper flex shrinking - Add flex-shrink-0 to sidebar toggle, h1, and SSE badge container - Update LibrarySearchFilter to use flex-1 with min/max constraints instead of fixed width when expanded, allowing it to shrink - Search now has min-w-[120px] to stay usable, max-w-48/64 to limit growth

Co-authored-by: armin.naimi <[email redacted]>