feat: enhance security with IP banning, ownership checks, and SSRF protection

Add comprehensive security improvements across the application:

- **IP-based login protection**: Implement IP ban system tracking login failures, auto-banning after threshold exceeded
- **Ownership verification**: Add userID parameter to Delete/Update operations for posts and comments to prevent unauthorized modifications
- **SSRF protection**: Add URL and resolved host validation for image URLs in chat and OpenAI client
- **SQL injection prevention**: Add EscapeLikeWildcard utility to escape special characters in LIKE queries
- **HTTP security**: Configure server timeouts and add security headers middleware
- **Rate limiting**: Refactor to support configurable duration and per-endpoint rate limits for auth routes
- **Error handling**: Standardize error responses using HandleError and proper error types

internal/pkg/openai/client.go

@@ -16,6 +16,8 @@ import (
 	"strings"
 	"time"
 
+	"with_you/internal/pkg/netutil"
+
 	xdraw "golang.org/x/image/draw"
 )
 
@@ -108,10 +110,8 @@ func NewClient(cfg Config) Client {
 		timeout = 30
 	}
 	return &clientImpl{
-		cfg: cfg,
-		httpClient: &http.Client{
-			Timeout: time.Duration(timeout) * time.Second,
-		},
+		cfg:        cfg,
+		httpClient: netutil.NewSafeHTTPClient(time.Duration(timeout) * time.Second),
 	}
 }
 
@@ -619,6 +619,9 @@ func (c *clientImpl) tryCompressImageForModeration(ctx context.Context, imageURL
 	if err != nil || (parsed.Scheme != "http" && parsed.Scheme != "https") {
 		return imageURL
 	}
+	if err := netutil.ValidateURL(imageURL); err != nil {
+		return imageURL
+	}
 
 	req, err := http.NewRequestWithContext(ctx, http.MethodGet, imageURL, nil)
 	if err != nil {