UI: gateway dashboard with glassmorphism theme system

Add a full-featured gateway dashboard UI built on Lit web components.

Shell & plumbing:
- App shell with router, controllers, and dependency wiring
- Login gate, i18n keys, and base layout scaffolding

Styles & theming:
- Base styles, chat styles, and responsive layout CSS
- 6-theme glassmorphism system (Obsidian, Aurora, Solar, etc.)
- Glass card, glass panel, and glass input components
- Favicon logo in expanded sidebar header

Views & features:
- Overview with attention cards, event log, quick actions, and log tail
- Chat view with markdown rendering, tool-call collapse, and delete support
- Command palette with fuzzy search
- Agent overview with config display, slash commands, and sidebar filtering
- Session list navigation and agent selector

Privacy & polish:
- Redact toggle with stream-mode default
- Blur host/IP in Connected Instances with reveal toggle
- Sensitive config value masking with count badge
- Card accent borders, hover lift effects, and responsive grid

.gitignore

@@ -17,6 +17,8 @@ __pycache__/
 ui/src/ui/__screenshots__/
 ui/playwright-report/
 ui/test-results/
+packages/dashboard-next/.next/
+packages/dashboard-next/out/
 
 # Mise configuration files
 mise.toml
@@ -101,3 +103,4 @@ package-lock.json
 apps/ios/LocalSigning.xcconfig
 # Generated protocol schema (produced via pnpm protocol:gen)
 dist/protocol.schema.json
+.ant-colony/