refactor: Standardize inventory data and naming conventions

This commit refactors the product inventory data to be a flat, single array. This design improves data versatility and scalability for various site functions.

- Flattened the data structure for easier filtering and searching.
- Atomized product attributes, such as `productNumber` and `skuID`.
- Standardized variable and object key naming to `camelCase` and `UPPERCASE_SNAKE_CASE` for constants.
- Added an `isFeatured` flag to products to enable dynamic content on the homepage.
- Implemented a meta tag in the base template to control search engine indexing on a per-page basis.

src/_data/testimonials.js

@@ -11,7 +11,7 @@
 }
 */
 
-const testimonials = [
+const TESTIMONIALS = [
     {
         "id": "T01",
         "clientName": "Caroline N.",
@@ -33,5 +33,5 @@ const testimonials = [
 ];
 
 module.exports = {
-    testimonials
+    TESTIMONIALS
 };