Add simplified pstn examples (#1822)

* Add simplified pstn examples
* Add daily_twilio_sip_dial_out example

examples/phone-chatbot/daily-pstn-dial-in/README.md

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+<!-- @format -->
+
+# Daily PSTN dial-in simple chatbot
+
+This project demonstrates how to create a voice bot that can receive phone calls via Dailys PSTN capabilities to enable voice conversations.
+
+## How It Works
+
+1. Daily receives an incoming call to your phone number.
+2. Daily calls your webhook server (`/start` endpoint).
+3. The server creates a Daily room with dial-in capabilities
+4. The server starts the bot process with the room details
+5. The caller is put on hold with music
+6. The bot joins the Daily room and signals readiness
+7. Daily forwards the call to the Daily room
+8. The caller and the bot are connected, and the bot handles the conversation
+
+## Prerequisites
+
+- A Daily account with an API key
+- An OpenAI API key for the bot's intelligence
+- A Cartesia API key for text-to-speech
+
+## Setup
+
+1. Create a virtual environment and install dependencies
+
+```bash
+python -m venv venv
+source venv/bin/activate  # On Windows: venv\Scripts\activate
+pip install -r requirements.txt
+```
+
+2. Set up environment variables
+
+Copy the example file and fill in your API keys:
+
+```bash
+cp .env.example .env
+# Edit .env with your API keys
+```
+
+3. Buy a phone number
+
+Instructions on how to do that can be found at this [docs link:](https://docs.daily.co/reference/rest-api/phone-numbers/buy-phone-number)
+
+4. Set up the dial-in config
+
+Instructions on how to do that can be found at this [docs link:](https://docs.daily.co/reference/rest-api/domainDialinConfig)
+
+5. For local testing, use ngrok to expose your local server
+
+```bash
+ngrok http 7860
+# Then use the provided URL (e.g., https://abc123.ngrok.io/start) in Twilio
+```
+
+## Running the Server
+
+Start the webhook server:
+
+```bash
+python server.py
+```
+
+## Testing
+
+Call the purchased phone number. The system should answer the call, put you on hold briefly, then connect you with the bot.
+
+## Customizing the Bot
+
+You can customize the bot's behavior by modifying the system prompt in `bot.py`.
+
+## Multiple SIP Endpoints
+
+For PSTN calls, you only need one SIP endpoint.
+
+## Daily SIP Configuration
+
+The bot configures Daily rooms with SIP capabilities using these settings:
+
+```python
+sip_params = DailyRoomSipParams(
+    display_name="phone-user",  # This will show up in the Daily UI; optional display the dialer's number
+    video=False,                # Audio-only call
+    sip_mode="dial-in",         # For receiving calls (vs. dial-out)
+    num_endpoints=1,            # Number of SIP endpoints to create
+)
+```
+
+## Troubleshooting
+
+### Call is not being answered
+
+- Check that your dial-in config is correctly configured to point towards your ngrok server and correct endpoint
+- Make sure the server.py file is running
+- Make sure ngrok is correctly setup and pointing to the correct port
+
+### Call connects but no bot is heard
+
+- Ensure your Daily API key is correct and has SIP capabilities
+- Verify that the Cartesia API key and voice ID are correct
+
+### Bot starts but disconnects immediately
+
+- Check the Daily logs for any error messages
+- Ensure your server has stable internet connectivity