Fix RBAC role system bugs and improve UX (#446)

* Fix RBAC role system bugs and improve UX

- Fix user list dropdown selection in host sharing
- Fix role sharing permissions to include role-based access
- Fix translation template interpolation for success messages
- Standardize system roles to admin and user only
- Auto-assign user role to new registrations
- Remove blocking confirmation dialogs in modal contexts
- Add missing i18n keys for common actions
- Fix button type to prevent unintended form submissions

* Enhance RBAC system with UI improvements and security fixes

- Move role assignment to Users tab with per-user role management
- Protect system roles (admin/user) from editing and manual assignment
- Simplify permission system: remove Use level, keep View and Manage
- Hide Update button and Sharing tab for view-only/shared hosts
- Prevent users from sharing hosts with themselves
- Unify table and modal styling across admin panels
- Auto-assign system roles on user registration
- Add permission metadata to host interface

* Add empty state message for role assignment

- Display helpful message when no custom roles available
- Clarify that system roles are auto-assigned
- Add noCustomRolesToAssign translation in English and Chinese

* fix: Prevent credential sharing errors for shared hosts

- Skip credential resolution for shared hosts with credential authentication
  to prevent decryption errors (credentials are encrypted per-user)
- Add warning alert in sharing tab when host uses credential authentication
- Inform users that shared users cannot connect to credential-based hosts
- Add translations for credential sharing warning (EN/ZH)

This prevents authentication failures when sharing hosts configured
with credential authentication while maintaining security by keeping
credentials isolated per user.

* feat: Improve rbac UI and fixes some bugs

---------

Co-authored-by: Luke Gustafson <88517757+LukeGus@users.noreply.github.com>
Co-authored-by: LukeGus <bugattiguy527@gmail.com>

src/backend/database/database.ts

@@ -8,6 +8,7 @@ import alertRoutes from "./routes/alerts.js";
 import credentialsRoutes from "./routes/credentials.js";
 import snippetsRoutes from "./routes/snippets.js";
 import terminalRoutes from "./routes/terminal.js";
+import rbacRoutes from "./routes/rbac.js";
 import cors from "cors";
 import fetch from "node-fetch";
 import fs from "fs";
@@ -1436,6 +1437,7 @@ app.use("/alerts", alertRoutes);
 app.use("/credentials", credentialsRoutes);
 app.use("/snippets", snippetsRoutes);
 app.use("/terminal", terminalRoutes);
+app.use("/rbac", rbacRoutes);
 
 app.use(
   (