modernize the codebase

Run the modernize linter across the codebase.
Change generated by running:

```
go run golang.org/x/tools/gopls/internal/analysis/modernize/cmd/modernize@latest -fix -test ./...
```

Ref:
https://pkg.go.dev/golang.org/x/tools/gopls/internal/analysis/modernize

internal/auth/jwt.go

@@ -2,6 +2,7 @@ package auth
 
 import (
 	"CatsOfMastodonBotGo/internal/config"
+	"maps"
 	"strings"
 	"time"
 
@@ -17,16 +18,14 @@ func NewJwtTokenGenerator(cfg *config.Config) *JwtTokenGenerator {
 	return &JwtTokenGenerator{cfg: cfg}
 }
 
-func (j *JwtTokenGenerator) GenerateToken(claims map[string]interface{}) (string, error) {
+func (j *JwtTokenGenerator) GenerateToken(claims map[string]any) (string, error) {
 	token := jwt.NewWithClaims(jwt.SigningMethodHS256, jwt.MapClaims{
 		"exp": time.Now().AddDate(0, 0, 1).Unix(),
 		"iat": time.Now().Unix(),
 		"iss": j.cfg.JwtIssuer,
 		"aud": j.cfg.JwtAudience,
 	})
-	for k, v := range claims {
-		token.Claims.(jwt.MapClaims)[k] = v
-	}
+	maps.Copy(token.Claims.(jwt.MapClaims), claims)
 
 	return token.SignedString([]byte(j.cfg.JwtSecret))
 }
@@ -41,7 +40,7 @@ func (j *JwtTokenGenerator) GinMiddleware() gin.HandlerFunc {
 		}
 
 		tokenString := strings.TrimPrefix(authHeader, "Bearer ")
-		t, err := jwt.Parse(tokenString, func(t *jwt.Token) (interface{}, error) {
+		t, err := jwt.Parse(tokenString, func(t *jwt.Token) (any, error) {
 			if _, ok := t.Method.(*jwt.SigningMethodHMAC); !ok {
 				return nil, jwt.ErrSignatureInvalid
 			}
@@ -61,4 +60,4 @@ func (j *JwtTokenGenerator) GinMiddleware() gin.HandlerFunc {
 
 		c.Next()
 	}
-}
+}