Source app About description from README and improve internal app READMEs (#22012)

## What

- The SDK manifest build now sources an app's `aboutDescription` (the
long-form "About" tab content) from its `README.md`. An explicit
`aboutDescription` in the config still wins, matching the existing
marketplace CDN fallback.
- Removed the now-duplicated `aboutDescription` from internal app
configs and deleted the standalone `ABOUT_DESCRIPTION` constant files.
- Rewrote internal app READMEs to read as user-facing About content:
stripped developer/build/source-path noise, and expanded the thin ones.
`call-recording` and `self-hosting` (one-liners over substantial apps)
and `people-data-labs` were rewritten from a close reading of the code;
`twenty-exa` was verified for accuracy.
- Added a unit test (and a fixture README) covering README →
`aboutDescription` in the build.

## Why

The README and the About description were maintained separately and
drifted. Making the README the single source keeps the About tab
accurate and removes duplicated copy.

## Notes for reviewers

- Internal apps depend on the published `twenty-sdk`, so the build
change takes effect for them after an SDK release + dependency bump.
Until then, published apps still get README → `aboutDescription` via the
marketplace CDN sync.
- Standard/Custom app descriptions are unchanged (they are resolved in
the frontend, not via the manifest).

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packages/twenty-server/src/engine/core-modules/application/application-marketplace/marketplace-catalog-sync.service.ts

@@ -42,27 +42,10 @@ export class MarketplaceCatalogSyncService {
         const universalIdentifier =
           fetchedManifest.application.universalIdentifier;
 
-        const aboutDescription =
-          fetchedManifest.application.aboutDescription ??
-          (await this.marketplaceService.fetchReadmeFromRegistryCdn(
-            pkg.name,
-            pkg.version,
-          ));
-
-        const manifest = aboutDescription
-          ? {
-              ...fetchedManifest,
-              application: {
-                ...fetchedManifest.application,
-                aboutDescription,
-              },
-            }
-          : fetchedManifest;
-
         const cdnBaseUrl = this.twentyConfigService.get('APP_REGISTRY_CDN_URL');
 
         const manifestWithResolvedUrls = resolveManifestAssetUrls(
-          manifest,
+          fetchedManifest,
           (filePath) =>
             buildRegistryCdnUrl({
               cdnBaseUrl,
@@ -74,7 +57,7 @@ export class MarketplaceCatalogSyncService {
 
         await this.applicationRegistrationService.upsertFromCatalog({
           universalIdentifier,
-          name: manifest.application.displayName ?? pkg.name,
+          name: fetchedManifest.application.displayName ?? pkg.name,
           sourceType: ApplicationRegistrationSourceType.NPM,
           sourcePackage: pkg.name,
           latestAvailableVersion: pkg.version ?? null,

packages/twenty-server/src/engine/core-modules/application/application-marketplace/marketplace.service.ts

@@ -73,39 +73,6 @@ export class MarketplaceService {
     }
   }
 
-  async fetchReadmeFromRegistryCdn(
-    packageName: string,
-    version: string,
-  ): Promise<string | null> {
-    const cdnBaseUrl = this.twentyConfigService.get('APP_REGISTRY_CDN_URL');
-    const url = buildRegistryCdnUrl({
-      cdnBaseUrl,
-      packageName,
-      version,
-      filePath: 'README.md',
-    });
-
-    try {
-      const { data } = await axios.get(url, {
-        headers: { 'User-Agent': 'Twenty-Marketplace' },
-        timeout: 5_000,
-        responseType: 'text',
-      });
-
-      if (!data || data.trim().length === 0) {
-        return null;
-      }
-
-      return data;
-    } catch {
-      this.logger.debug(
-        `Could not fetch README from CDN for ${packageName}@${version}`,
-      );
-
-      return null;
-    }
-  }
-
   async fetchAppsFromRegistry(): Promise<RegistryPackageInfo[]> {
     const registryUrl = this.twentyConfigService.get('APP_REGISTRY_URL');