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/handler/post_handler.go

@@ -496,9 +496,9 @@ func (h *PostHandler) Delete(c *gin.Context) {
 		return
 	}
 
-	err = h.postService.Delete(c.Request.Context(), id)
+	err = h.postService.Delete(c.Request.Context(), userID, id)
 	if err != nil {
-		response.InternalServerError(c, "failed to delete post")
+		response.HandleError(c, err, "failed to delete post")
 		return
 	}