chore: run go fix for Go 1.26 modernization

106 files: interface{}→any, strings.Split→SplitSeq, CutPrefix/Cut, strings.Builder, slices.Contains, remove redundant // +build directives, gofmt import ordering and indentation.

Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-openagent)

Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>

backend/auth/jwt.go

@@ -121,7 +121,7 @@ func GenerateToken(userID string, role string) (string, string, error) {
 		return "", "", err
 	}
 
-	_, tokenString, err := TokenAuth.Encode(map[string]interface{}{
+	_, tokenString, err := TokenAuth.Encode(map[string]any{
 		"user_id": userID,
 		"role":    role,
 		"jti":     jti,
@@ -137,7 +137,7 @@ func VerifyToken(tokenString string, ctx context.Context) (userID string, role s
 		return "", "", "", err
 	}
 
-	var uidVal interface{}
+	var uidVal any
 	if err := token.Get("user_id", &uidVal); err != nil {
 		return "", "", "", fmt.Errorf("invalid user_id claim")
 	}
@@ -146,7 +146,7 @@ func VerifyToken(tokenString string, ctx context.Context) (userID string, role s
 		return "", "", "", fmt.Errorf("invalid user_id claim")
 	}
 
-	var roleVal interface{}
+	var roleVal any
 	if err := token.Get("role", &roleVal); err != nil {
 		return "", "", "", fmt.Errorf("invalid role claim")
 	}
@@ -155,7 +155,7 @@ func VerifyToken(tokenString string, ctx context.Context) (userID string, role s
 		return "", "", "", fmt.Errorf("invalid role claim")
 	}
 
-	var jtiVal interface{}
+	var jtiVal any
 	if err := token.Get("jti", &jtiVal); err != nil {
 		return "", "", "", fmt.Errorf("invalid jti claim")
 	}

backend/auth/jwt_test.go

@@ -1,5 +1,4 @@
 //go:build test
-// +build test
 
 package auth
 

backend/auth/testmain_test.go

@@ -1,5 +1,4 @@
 //go:build test
-// +build test
 
 package auth