feat(sdk): use config file as single source of truth, remove env var fallbacks (#19409)

## Summary

- **Config as source of truth**: `~/.twenty/config.json` is now the
single source of truth for SDK authentication — env var fallbacks have
been removed from the config resolution chain.
- **Test instance support**: `twenty server start --test` spins up a
dedicated Docker instance on port 2021 with its own config
(`config.test.json`), so integration tests don't interfere with the dev
environment.
- **API key auth for marketplace**: Removed `UserAuthGuard` from
`MarketplaceResolver` so API key tokens (workspace-scoped) can call
`installMarketplaceApp`.
- **CI for example apps**: Added monorepo CI workflows for `hello-world`
and `postcard` example apps to catch regressions.
- **Simplified CI**: All `ci-create-app-e2e` and example app workflows
now use a shared `spawn-twenty-app-dev-test` action (Docker-based)
instead of building the server from source. Consolidated auth env vars
to `TWENTY_API_URL` + `TWENTY_API_KEY`.
- **Template publishing fix**: `create-twenty-app` template now
correctly preserves `.github/` and `.gitignore` through npm publish
(stored without leading dot, renamed after copy).

## Test plan

- [x] CI SDK (lint, typecheck, unit, integration, e2e) — all green
- [x] CI Example App Hello World — green
- [x] CI Example App Postcard — green
- [x] CI Create App E2E minimal — green
- [x] CI Front, CI Server, CI Shared — green

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

@@ -12,7 +12,6 @@ import { WorkspaceEntity } from 'src/engine/core-modules/workspace/workspace.ent
 import { AuthWorkspace } from 'src/engine/decorators/auth/auth-workspace.decorator';
 import { NoPermissionGuard } from 'src/engine/guards/no-permission.guard';
 import { SettingsPermissionGuard } from 'src/engine/guards/settings-permission.guard';
-import { UserAuthGuard } from 'src/engine/guards/user-auth.guard';
 import { WorkspaceAuthGuard } from 'src/engine/guards/workspace-auth.guard';
 import { MarketplaceCatalogSyncCronJob } from 'src/engine/core-modules/application/application-marketplace/crons/marketplace-catalog-sync.cron.job';
 import { InjectMessageQueue } from 'src/engine/core-modules/message-queue/decorators/message-queue.decorator';
@@ -21,7 +20,7 @@ import { MessageQueueService } from 'src/engine/core-modules/message-queue/servi
 
 @MetadataResolver()
 @UseFilters(ApplicationRegistrationExceptionFilter)
-@UseGuards(UserAuthGuard, WorkspaceAuthGuard, NoPermissionGuard)
+@UseGuards(WorkspaceAuthGuard, NoPermissionGuard)
 export class MarketplaceResolver {
   constructor(
     private readonly marketplaceQueryService: MarketplaceQueryService,