fix: eliminate magic strings and fix aggregate boundary detection

- Extract DDD folder names and repository method suggestions to constants
- Fix regex pattern to support relative paths (domain/... without leading /)
- Add non-aggregate folder exclusions (constants, shared, factories, etc.)
- Remove findAll, exists, count from ORM_QUERY_METHODS (valid domain methods)
- Add exists, count, countBy patterns to domainMethodPatterns
- Add aggregate boundary test examples

packages/guardian/examples/aggregate-boundary/domain/aggregates/product/Product.ts

@@ -0,0 +1,7 @@
+export class Product {
+    public price: number
+
+    constructor(price: number) {
+        this.price = price
+    }
+}