fix(datastore/postgres/gcp-cloudsql): read project_id, not project (#366)

The three GCP datastore modules consume the same @facets/gcp_cloud_account
provider input, but postgres/gcp-cloudsql declared the attribute as `project`
while mysql/gcp-cloudsql and redis/gcp-memorystore use `project_id`. Both work
today only because the resource-type system passes the whole interface object;
the drift breaks the moment the output schema is tightened to one canonical
name. Align on project_id (matches the two siblings and GCP API naming).

Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: srikxcipher

modules/datastore/postgres/gcp-cloudsql/1.0/variables.tf

@@ -82,7 +82,7 @@ variable "inputs" {
   type = object({
     gcp_provider = object({
       attributes = object({
-        project     = string
+        project_id  = string
         credentials = string
       })
     })