Add comprehensive test coverage for services and utilities

Co-Authored-By: Claude Haiku 4.5 <noreply@anthropic.com>

src/lib/utils/validation.ts

@@ -88,17 +88,20 @@ export function validateUrlPathSegment(segment: string): void {
  * Validate numeric parameter (width, height, quality, etc.)
  */
 export function validateNumericParam(value: unknown, min = 0, max = 10000, name = "parameter"): number {
-  const num = Number(value);
-
-  if (!Number.isInteger(num)) {
+  // Must be an actual number, not a string that looks like a number
+  if (typeof value !== "number") {
     throw new Error(`Invalid ${name}: must be an integer`);
   }
 
-  if (num < min || num > max) {
+  if (!Number.isInteger(value)) {
+    throw new Error(`Invalid ${name}: must be an integer`);
+  }
+
+  if (value < min || value > max) {
     throw new Error(`Invalid ${name}: must be between ${min} and ${max}`);
   }
 
-  return num;
+  return value;
 }
 
 /**