Add simplified pstn examples (#1822)

* Add simplified pstn examples
* Add daily_twilio_sip_dial_out example

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

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+# Daily PSTN dial-out simple chatbot
+
+This project demonstrates how to create a voice bot that uses Dailys PSTN capabilities to make calls to phone numbers.
+
+## How it works
+
+1. The server file receives a curl request with the phone number to dial out to
+2. The server creates a Daily room with SIP capabilities
+3. The server starts the bot process with the room details
+4. When the bot has joined, it starts the dial-out process and rings the number provided in the curl request
+5. The user then answers the phone and the user is brought into the call
+6. The end user and bot are connected, and the bot handles the conversation
+
+## Prerequisites
+
+- A Daily account with an API key, and a phone number purchased through Daily
+- A US phone number to ring
+- dial-out must be enabled on your domain. Find out more by reading this [document and filling in the form](https://docs.daily.co/guides/products/dial-in-dial-out#main)
+- OpenAI API key for the bot's intelligence
+- 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. Request dial-out enablement
+
+For compliance reasons, to enable dial-out for your Daily account, you must request enablement via the form. You can find out more about dial-out, and the form at the [link here:](https://docs.daily.co/guides/products/dial-in-dial-out#main)
+
+## Running the Server
+
+Start the webhook server:
+
+```bash
+python server.py
+```
+
+## Testing
+
+With server.py running, send the following curl command from your terminal:
+
+```bash
+curl -X POST "http://127.0.0.1:7860/start" \
+  -H "Content-Type: application/json" \
+  -d '{
+    "dialout_settings": {
+      "phone_number": "+12345678910"
+    }
+  }'
+```
+
+The server should make a room. The bot will join the room and then ring the number provided. Answer the call to speak 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 dial-out configuration
+
+The bot configures the Daily rooms with dial-out capabilities using these settings. Note: You also need dial-out to be enabled on the domain, as mentioned earlier on in the README.
+
+```python
+properties = DailyRoomProperties(
+        sip=sip_params,
+        enable_dialout=True,  # Needed for outbound calls if you expand the bot
+        enable_chat=False,  # No need for chat in a voice bot
+        start_video_off=True,  # Voice only
+)
+```
+
+## Troubleshooting
+
+### I get an error about dial-out not being enabled
+
+- Check that your room has `enable_dialout=True` set
+- Check that your meeting token is an owner token (The bot does this for you automatically)
+- Check that you have purchased a phone number to ring from
+- Check that the phone number you are trying to ring is correct, and is a US or Canadian number.
+
+### 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