feat: add admin login page and authentication API

- Created a new login page for admin access at frontend/admin/login/index.html.
- Implemented form submission with error handling for login credentials.
- Updated frontend/index.html to mute the video player and removed unnecessary Alpine.js data binding.
- Enhanced manifest URL resolution in frontend/src/main.ts to include cache-busting parameters.
- Modified vite.config.ts to include the new admin login page in the build process.
- Updated nginx.conf to handle admin login routing, authentication, and API proxying for admin actions.

CHANGELOG.md

@@ -2,6 +2,20 @@
 
 <!-- markdownlint-disable MD024 -->
 
+## [1.0.3] - 2026-08-03
+
+### Added
+
+- Added Prometheus-format `/metrics` endpoint for chat runtime and admin-session monitoring.
+
+### Changed
+
+- Updated Prometheus scrape targets and Grafana dashboard queries to use live chat metrics.
+
+### Fixed
+
+- Fixed nginx routing so `/metrics` is reachable through localhost and `linearvoid.tv`.
+
 ## [1.0.2] - 2026-08-03
 
 ### Changed