fix(shared): link-field where query must use (customer.Id,eq,N) not (customer,eq,N)

- calculateEffectiveGrants queried CustomerProducts/AccessGrants with
  (customer,eq,N), which matches the link field's DISPLAY NAME and always
  returns 0 rows -> desiredPaths always [] -> W1/W2/W3 write empty scopes.
- Regression from the shared-lib refactor (3ecee30): W2 had already fixed
  this in 36a6b3b but the shared extract reverted to the old syntax.
- Correct syntax (customer.Id,eq,N) verified against live NocoDB for
  customer 6 -> /Class/Health, /Class/Other, /Template/Music.
- Updated all three test mocks to match the corrected where clause.

n8n/test_effective_grants.js

@@ -64,11 +64,11 @@ function makeCtx() {
         }
         if (u.includes('/tr/records?limit=10000')) return { list: RESOURCES };
         // CustomerProducts where customer eq
-        if (u.includes('/tcpc/records?where=(customer,eq,')) {
+        if (u.includes('/tcpc/records?where=(customer.Id,eq,')) {
           return { list: CUSTOMERPRODUCTS };
         }
         // AccessGrants where customer eq
-        if (u.includes('/tag/records?where=(customer,eq,')) {
+        if (u.includes('/tag/records?where=(customer.Id,eq,')) {
           return { list: ACCESSGRANTS };
         }
         // Product M2M link