Security: add rate limiting, input validation, and filter category

validation
Backend:
- Add rate limiting middleware (mw/ratelimit.go) - in-memory per-IP
  limiter
- Apply rate limits per endpoint group:
  - Public read-only: 120/min
  - Registration: 10/min
  - Portfolio filters: 60/min
  - Authenticated users: 120/min
  - Admin: none (trusted)
- Add 256 char input length validation on portfolio endpoints
- Validate filter categories exist in DB before querying
- Secure GetImage endpoint: only allow UUID or numeric timestamp (15-20
  digits)
- Remove pattern-based image lookup to prevent enumeration
- Add services validation: name (100), duration (1-480), patch test
  (0-168)
  Frontend:
- Add maxlength=256 to portfolio tag/search inputs
- Add maxlength to registration: name (50), email (255), phone (20),
  password (72)
- Add maxlength=100 to service name input

backend/handlers/portfolio/images.go

@@ -20,6 +20,38 @@ import (
 	"github.com/go-chi/chi/v5"
 )
 
+const MaxInputLength = 256
+
+// validateInputLength returns an error if input exceeds max length
+func validateInputLength(input string) error {
+	if len(input) > MaxInputLength {
+		return fmt.Errorf("input exceeds maximum length of %d characters", MaxInputLength)
+	}
+	return nil
+}
+
+// getAllowedCategories fetches all unique category prefixes from existing tags
+func getAllowedCategories(ctx context.Context) (map[string]bool, error) {
+	rows, err := db.DB.Query(ctx, `
+		SELECT DISTINCT SPLIT_PART(t, ':', 1) as category
+		FROM images, unnest(tag_names) as t
+		WHERE t LIKE '%:%'
+	`)
+	if err != nil {
+		return nil, err
+	}
+	defer rows.Close()
+
+	categories := make(map[string]bool)
+	for rows.Next() {
+		var cat string
+		if err := rows.Scan(&cat); err == nil && cat != "" {
+			categories[cat] = true
+		}
+	}
+	return categories, nil
+}
+
 type Image struct {
 	ID           string    `json:"id"`
 	URL          string    `json:"url"`
@@ -36,6 +68,21 @@ type Tag struct {
 func ListImages(w http.ResponseWriter, r *http.Request) {
 	tagFilter := r.URL.Query().Get("tag")
 	tagsFilter := r.URL.Query().Get("tags")
+
+	// Validate input length
+	if tagFilter != "" {
+		if err := validateInputLength(tagFilter); err != nil {
+			http.Error(w, err.Error(), http.StatusBadRequest)
+			return
+		}
+	}
+	if tagsFilter != "" {
+		if err := validateInputLength(tagsFilter); err != nil {
+			http.Error(w, err.Error(), http.StatusBadRequest)
+			return
+		}
+	}
+
 	limit := 20
 	offset := 0
 
@@ -50,6 +97,14 @@ func ListImages(w http.ResponseWriter, r *http.Request) {
 		}
 	}
 
+	// Validate filter categories against allowed list from DB
+	allowedCategories, err := getAllowedCategories(r.Context())
+	if err != nil {
+		log.Printf("Failed to get allowed categories: %v", err)
+		http.Error(w, "Internal server error", http.StatusInternalServerError)
+		return
+	}
+
 	filterClauses := ""
 	filterArgs := []interface{}{}
 
@@ -63,6 +118,18 @@ func ListImages(w http.ResponseWriter, r *http.Request) {
 			if len(matches) == 2 {
 				category := matches[1]
 				value := values[0]
+
+				// Validate category exists
+				if !allowedCategories[category] {
+					continue // Skip invalid categories silently for backward compatibility
+				}
+
+				// Validate input length
+				if err := validateInputLength(category + ":" + value); err != nil {
+					http.Error(w, err.Error(), http.StatusBadRequest)
+					return
+				}
+
 				filterClauses += fmt.Sprintf(" AND $%d = ANY(tag_names)", len(filterArgs)+1)
 				filterArgs = append(filterArgs, category+":"+value)
 			}
@@ -620,7 +687,15 @@ func extractKey(url string) string {
 func GetImage(w http.ResponseWriter, r *http.Request) {
 	imageID := chi.URLParam(r, "id")
 
+	// Validate input length
+	if err := validateInputLength(imageID); err != nil {
+		http.Error(w, err.Error(), http.StatusBadRequest)
+		return
+	}
+
 	var img Image
+
+	// First try UUID lookup
 	err := db.DB.QueryRow(r.Context(), `
 		SELECT id, url, thumbnail_url, tag_names, created_at 
 		FROM images 
@@ -628,17 +703,20 @@ func GetImage(w http.ResponseWriter, r *http.Request) {
 	`, imageID).Scan(&img.ID, &img.URL, &img.ThumbnailURL, (*[]string)(&img.TagNames), &img.CreatedAt)
 
 	if err != nil {
-		// Try to find by URL if UUID lookup failed
-		// This allows using timestamps/keys from S3 URLs
-		searchPattern := "%" + imageID + "%"
-		err = db.DB.QueryRow(r.Context(), `
-			SELECT id, url, thumbnail_url, tag_names, created_at 
-			FROM images 
-			WHERE url LIKE $1 OR thumbnail_url LIKE $1
-			LIMIT 1
-		`, searchPattern).Scan(&img.ID, &img.URL, &img.ThumbnailURL, (*[]string)(&img.TagNames), &img.CreatedAt)
+		// If UUID lookup fails, try timestamp lookup (for ?img=timestamp from frontend)
+		// Only allow numeric timestamps (nanosecond Unix epoch) to prevent pattern enumeration
+		timestampMatch, _ := regexp.Compile(`^\d{15,20}$`)
+		if timestampMatch.MatchString(imageID) {
+			searchPattern := "%" + imageID + ".%"
+			err = db.DB.QueryRow(r.Context(), `
+				SELECT id, url, thumbnail_url, tag_names, created_at 
+				FROM images 
+				WHERE url LIKE $1 OR thumbnail_url LIKE $1
+				LIMIT 1
+			`, searchPattern).Scan(&img.ID, &img.URL, &img.ThumbnailURL, (*[]string)(&img.TagNames), &img.CreatedAt)
+		}
 
-		if err != nil {
+		if err != nil || !timestampMatch.MatchString(imageID) {
 			log.Printf("Failed to get image: %v", err)
 			http.Error(w, "Image not found", http.StatusNotFound)
 			return