[Bug] TypeScript quickstart samples broken: outdated SDK, hardcoded values, incorrect module config

Problem

The TypeScript quickstart samples (agent-service, chat-with-agent, create-agent, responses) have several
issues that prevent users from running them successfully:

1. Outdated SDK version — @azure/ai-projects is pinned to 1.0.0, but the code uses APIs (e.g.,
   agents.createVersion, responses.create) that require 2.x.

2. Hardcoded placeholder values — Some samples use hardcoded strings like "your_project_endpoint" and
   "gpt-5-mini" instead of reading from environment variables, inconsistent with the .env-template provided.

3. Missing dotenv/config import — chat-with-agent, create-agent, and responses don't import
   dotenv/config, so .env-template values are never loaded.

4. Verbose env var names — .env-template uses AZURE_AI_PROJECT_ENDPOINT / AZURE_AI_FOUNDRY_AGENT_NAME /
   AZURE_AI_FOUNDRY_MODEL_DEPLOYMENT_NAME but the code references shorter names, causing a mismatch.

5. Outdated tsconfig module resolution — Using "module": "ESNext" + "moduleResolution": "node" which doesn't
   align with modern Node.js ESM usage.

Expected Behavior

Users should be able to clone a quickstart, copy .env-template to .env, fill in their values, and run the sample
without additional troubleshooting.

PR link

https://github.com/microsoft-foundry/foundry-samples/pull/733