Add comprehensive OIDC access control and admin role mapping

Implements full OIDC configuration UI and backend support for access control and admin permissions.

**Access Control Features:**
- Open access (anyone can log in)
- Group/claim based access (require specific group membership)
- Allowed list (whitelist specific emails/usernames)
- Admin approval (manual approval required for new users)

**Admin Role Mapping:**
- Automatic admin role assignment based on OIDC claims
- Configurable claim name and value (default: groups claim)
- First user always becomes admin
- Dynamic role updates on each login

**Setup Wizard:**
- Updated OIDCConfigStep with comprehensive OIDC settings
- Access control method selector with conditional fields
- Admin role mapping configuration with examples
- Improved UX with clear sections and helpful descriptions

**Admin Settings:**
- Expanded OIDC section with all new configuration options
- Proper JSON array handling for allowed emails/usernames
- Visual organization matching setup wizard

**Backend:**
- Updated setup complete API to persist new OIDC fields
- Updated OIDC settings API for all new configuration
- Updated settings GET endpoint to return new fields with defaults
- Proper comma-separated to JSON array conversion

**Documentation:**
- Comprehensive OIDC section in auth.md
- Configuration examples and use cases
- Clear distinction between access control and admin roles
- Default values documented

All changes tested and ready for production use.

src/app/api/admin/settings/oidc/route.ts

@@ -11,7 +11,21 @@ export async function PUT(request: NextRequest) {
     return requireAdmin(req, async () => {
       try {
         const body = await request.json();
-        const { enabled, providerName, issuerUrl, clientId, clientSecret } = body;
+        const {
+          enabled,
+          providerName,
+          issuerUrl,
+          clientId,
+          clientSecret,
+          accessControlMethod,
+          accessGroupClaim,
+          accessGroupValue,
+          allowedEmails,
+          allowedUsernames,
+          adminClaimEnabled,
+          adminClaimName,
+          adminClaimValue,
+        } = body;
 
         const { getConfigService } = await import('@/lib/services/config.service');
         const configService = getConfigService();
@@ -22,6 +36,14 @@ export async function PUT(request: NextRequest) {
           { key: 'oidc.provider_name', value: providerName || '' },
           { key: 'oidc.issuer_url', value: issuerUrl || '' },
           { key: 'oidc.client_id', value: clientId || '' },
+          { key: 'oidc.access_control_method', value: accessControlMethod || 'open' },
+          { key: 'oidc.access_group_claim', value: accessGroupClaim || 'groups' },
+          { key: 'oidc.access_group_value', value: accessGroupValue || '' },
+          { key: 'oidc.allowed_emails', value: allowedEmails || '[]' },
+          { key: 'oidc.allowed_usernames', value: allowedUsernames || '[]' },
+          { key: 'oidc.admin_claim_enabled', value: adminClaimEnabled ? 'true' : 'false' },
+          { key: 'oidc.admin_claim_name', value: adminClaimName || 'groups' },
+          { key: 'oidc.admin_claim_value', value: adminClaimValue || '' },
         ];
 
         // Only update client secret if provided (not masked)