Add OIDC provider functionality with validation setup

This commit adds OpenID Connect (OIDC) provider functionality to tinyauth,
allowing it to act as an OIDC identity provider for other applications.

Features:
- OIDC discovery endpoint at /.well-known/openid-configuration
- Authorization endpoint for OAuth 2.0 authorization code flow
- Token endpoint for exchanging authorization codes for tokens
- ID token generation with JWT signing
- JWKS endpoint for public key distribution
- Support for PKCE (code challenge/verifier)
- Nonce validation for ID tokens
- Configurable OIDC clients with redirect URIs, scopes, and grant types

Validation:
- Docker Compose setup for local testing
- OIDC test client (oidc-whoami) with session management
- Nginx reverse proxy configuration
- DNS server (dnsmasq) for custom domain resolution
- Chrome launch script for easy testing

Configuration:
- OIDC configuration in config.yaml
- Example configuration in config.example.yaml
- Database migrations for OIDC client storage

internal/bootstrap/router_bootstrap.go

@@ -102,5 +102,15 @@ func (app *BootstrapApp) setupRouter() (*gin.Engine, error) {
 
 	healthController.SetupRoutes()
 
+	// Setup OIDC controller if OIDC is enabled
+	if app.config.OIDC.Enabled && app.services.oidcService != nil {
+		oidcController := controller.NewOIDCController(controller.OIDCControllerConfig{
+			AppURL:      app.config.AppURL,
+			CookieDomain: app.context.cookieDomain,
+		}, apiRouter, app.services.oidcService, app.services.authService)
+
+		oidcController.SetupRoutes()
+	}
+
 	return engine, nil
 }