feat: add minimal feed_audio example for testing without hardware

[Muhammad-Awab]

This PR adds a minimal example demonstrating how to use SAA's feed_audio() with generated audio.

Changes

• New file: examples/python/minimal_example.py
• Shows how to use SAA in feed mode (enable_audio=False)
• Includes a simple test tone generator
• Uses on_turn_ready and on_warmup_complete callbacks

Why this is useful

• Testing SAA without a microphone
• CI/CD pipelines
• Quick validation of SAA functionality
• Reference for integrating with Twilio Media Streams

How to test

# Set your API key
export SAA_API_KEY=your_key_here

Run the example

python examples/python/minimal_example.py

[omarthen3rd]

Do not to hardcode the warmup, SAA still needs audio fed during warmup phase.
Also no emojis in code.