fix(signin): float dropdown above footer + no-cache dev headers
- Remove the trapping z-index on .signin-form-preview-wrap; the wrap was
creating its own stacking context, so the dropdown's z-index could not
rise above sibling page chrome (logo, footer links).
- Lift the form's .glass card on /explore/create with z-index:50 so its
whole subtree (including the dropdown anchored inside it) paints above
the later-in-DOM footer instead of being covered by it.
- Restore the lightly translucent glass surface for the dropdown now
that stacking is correct.
- Add no-store/Cache-Control headers and explicit hmr port to the Vite
dev server so CSS / island / route changes reflect on the next request
without manual hard refresh.
Made-with: Cursor