chore: improve monitoring for Race condition between cache invalidation of flat

**Monitoring improvement:** Added structured logging to `WorkspaceSchemaFactory` that records key diagnostic context on every schema build:
- Whether typeDefs were served from cache or freshly generated
- The `metadataVersion` used for the cache key
- The number of objects in `flatObjectMetadataMaps`

This log line fires on every `POST /graphql` request and provides the exact data needed to diagnose future cache desync issues. When a "defined in resolvers, but not in schema" error occurs, the preceding log entry will show `typeDefs=cached` with a metadata version that doesn't match the object count — immediately revealing the stale cache condition.

Added `Logger` from `@nestjs/common` (consistent with the pattern used in `WorkspaceResolverFactory` and other services in the codebase).

packages/twenty-server/src/engine/api/graphql/workspace-schema.factory.ts

@@ -1,4 +1,4 @@
-import { Injectable } from '@nestjs/common';
+import { Injectable, Logger } from '@nestjs/common';
 
 import { makeExecutableSchema } from '@graphql-tools/schema';
 import { GraphQLSchema, printSchema } from 'graphql';
@@ -27,6 +27,8 @@ import { TWENTY_STANDARD_APPLICATION } from 'src/engine/workspace-manager/twenty
 
 @Injectable()
 export class WorkspaceSchemaFactory {
+  private readonly logger = new Logger(WorkspaceSchemaFactory.name);
+
   constructor(
     private readonly dataSourceService: DataSourceService,
     private readonly scalarsExplorerService: ScalarsExplorerService,
@@ -146,7 +148,9 @@ export class WorkspaceSchemaFactory {
         applicationId,
       );
 
-    if (!typeDefs || !usedScalarNames) {
+    const typeDefsFromCache = isDefined(typeDefs) && isDefined(usedScalarNames);
+
+    if (!typeDefsFromCache) {
       const autoGeneratedSchema =
         await this.workspaceGraphQLSchemaGenerator.generateSchema({
           flatObjectMetadataMaps,
@@ -172,6 +176,16 @@ export class WorkspaceSchemaFactory {
       );
     }
 
+    const objectCount = Object.keys(
+      flatObjectMetadataMaps.byUniversalIdentifier,
+    ).length;
+
+    this.logger.log(
+      `Building schema for workspace ${workspace.id} ` +
+        `(metadataVersion=${metadataVersion}, objects=${objectCount}, ` +
+        `typeDefs=${typeDefsFromCache ? 'cached' : 'generated'})`,
+    );
+
     const autoGeneratedResolvers = await this.workspaceResolverFactory.create(
       flatObjectMetadataMaps,
       flatFieldMetadataMaps,