Release extension 0.1.1: kit 1.0 lib, shield logo icons ...

Rebuild both browsers' packages against gnexus-ui-kit 1.0 (make lib
from frontend/node_modules) and swap the generic dots mark for the
shield keyhole logo rasterized from frontend/public/logo.svg
(icon.svg + 16/32/48/128 PNG rsvg-convert). Popup verified in
chromium: settings drawer and secrets list render with no page errors.
Version bumped in extension manifest + Makefile; extensions/manifest.json
points at the 0.1.1 zips with fresh sha256/size (0.1.0 zips removed).

Co-Authored-By: Claude Code <noreply@anthropic.com>

Refresh extension builds (split Chrome/Firefox) ...

Repackage the Chrome and Firefox builds from the extension repo and
update extensions/manifest.json checksums, sizes, and release date.

Co-Authored-By: Claude <noreply@anthropic.com>

Add in-app extension download page ...

Distribute the gnexus-creds browser extension from the service itself.
Package Chrome and Firefox builds into extensions/dist/ with a manifest
describing version, checksums, and sizes; serve them via authenticated
FastAPI endpoints and surface a new Extension tab in the Vue UI with
download cards, SHA-256, and install instructions.

Co-Authored-By: Claude <noreply@anthropic.com>