Add complete multi-user support with role-based access control:
Backend:
- Add users CRUD endpoints (GET/POST/PUT/DELETE /api/users) with admin-only guards
- Add display_name column to users table with ALTER TABLE migration
- Fix auth to use session-based user identity (not hardcoded 'admin')
- Add POST /api/auth/logout to revoke server-side sessions
- Add require_admin() and extract_session() helpers for clean RBAC
- Guard all mutating endpoints (clients, providers, models, settings, backup)
Frontend:
- Add Users management page with create/edit/reset-password/delete modals
- Add role gating: hide edit/delete buttons for viewers on clients, providers, models
- Settings page hides auth tokens and admin actions for viewers
- Logout now revokes server session before clearing localStorage
- Sidebar shows real display_name and formatted role (Administrator/Viewer)
- Fix sidebar header: single logo with onerror fallback, renamed to 'LLM Proxy'
- Add badge and btn-action CSS classes for role pills and action buttons
- Bump cache-bust to v=7
- Added 'credit_balance' and 'low_credit_threshold' to 'provider_configs' table.
- Updated dashboard backend to support reading and updating provider credits.
- Implemented real-time credit deduction from provider balances on successful requests.
- Added visual balance indicators and configuration modal to the 'Providers' dashboard tab.
- Added 'provider_configs' and 'model_configs' tables to database.
- Refactored ProviderManager to support thread-safe dynamic updates and database overrides.
- Implemented 'Models' tab in dashboard to manage model visibility, mapping, and pricing.
- Added provider configuration modal to 'Providers' tab.
- Integrated database overrides into chat completion logic (enabled state, mapping, and cost).
- Switched from mock data to real backend APIs.
- Implemented unified ApiClient for consistent frontend data fetching.
- Refactored dashboard structure and styles for a modern SaaS aesthetic.
- Fixed Axum 0.8+ routing and parameter syntax issues.
- Implemented real client creation/deletion and provider health monitoring.
- Synchronized WebSocket event structures between backend and frontend.
