auth: enable JWT validation, support roles claim

- Enable auth in gateway config with JWKS URL
- Check both 'permissions' (users) and 'roles' (service accounts)
- Allow any Authentik issuer (service accounts have per-provider issuers)
- Required capability: llm:inference

internal/auth/jwt.go

@@ -3,6 +3,7 @@ package auth
 import (
 	"context"
 	"fmt"
+	"strings"
 	"sync"
 	"time"
 
@@ -107,42 +108,64 @@ func (v *Validator) ValidateBearerToken(authHeader string) (jwt.MapClaims, error
 		}
 	}
 
-	// Check iss (issuer)
-	if iss, ok := claims["iss"].(string); !ok || iss != v.issuer {
-		return nil, fmt.Errorf("invalid issuer: expected %s, got %s", v.issuer, iss)
+	// Check iss (issuer) - if configured, must match exactly or be from Authentik
+	// Service accounts have per-provider issuers, so we allow any authentik.riotpiao.com issuer
+	if v.issuer != "" {
+		iss, ok := claims["iss"].(string)
+		if !ok {
+			return nil, fmt.Errorf("missing issuer claim")
+		}
+		// Allow exact match or any Authentik issuer
+		if iss != v.issuer && !isAuthentikIssuer(iss) {
+			return nil, fmt.Errorf("invalid issuer: expected %s or Authentik, got %s", v.issuer, iss)
+		}
 	}
 
-	// Check aud (audience)
-	if aud, ok := claims["aud"].(string); !ok || aud != v.audience {
-		return nil, fmt.Errorf("invalid audience: expected %s, got %s", v.audience, aud)
+	// Check aud (audience) - if configured, must match
+	if v.audience != "" {
+		if aud, ok := claims["aud"].(string); !ok || aud != v.audience {
+			return nil, fmt.Errorf("invalid audience: expected %s, got %s", v.audience, aud)
+		}
 	}
 
 	return claims, nil
 }
 
 // CheckPermissions checks if claims contain required permission(s).
+// Checks both "permissions" (user tokens) and "roles" (service account tokens).
 // Returns true if any required permission is found or wildcard "*" exists.
 func (v *Validator) CheckPermissions(claims jwt.MapClaims, required ...string) bool {
-	permsIface, ok := claims["permissions"]
+	// Check both claims - users have "permissions", service accounts have "roles"
+	for _, claimKey := range []string{"permissions", "roles"} {
+		if v.checkClaimList(claims, claimKey, required...) {
+			return true
+		}
+	}
+	return false
+}
+
+// checkClaimList checks if a specific claim contains any required value.
+func (v *Validator) checkClaimList(claims jwt.MapClaims, claimKey string, required ...string) bool {
+	valuesIface, ok := claims[claimKey]
 	if !ok {
 		return false
 	}
 
-	perms, ok := permsIface.([]interface{})
+	values, ok := valuesIface.([]interface{})
 	if !ok {
 		return false
 	}
 
-	for _, perm := range perms {
-		permStr, ok := perm.(string)
+	for _, val := range values {
+		valStr, ok := val.(string)
 		if !ok {
 			continue
 		}
-		if permStr == "*" {
+		if valStr == "*" {
 			return true
 		}
 		for _, req := range required {
-			if permStr == req {
+			if valStr == req {
 				return true
 			}
 		}
@@ -151,6 +174,13 @@ func (v *Validator) CheckPermissions(claims jwt.MapClaims, required ...string) b
 	return false
 }
 
+// isAuthentikIssuer checks if issuer is from our Authentik instance.
+func isAuthentikIssuer(iss string) bool {
+	return len(iss) > 0 && 
+		(iss == "https://authentik.riotpiao.com" ||
+		 strings.HasPrefix(iss, "https://authentik.riotpiao.com/"))
+}
+
 // DecodeToken decodes JWT payload without verification (for debugging/testing).
 func DecodeToken(tokenString string) (jwt.MapClaims, error) {
 	claims := jwt.MapClaims{}