Add thermocycler quickstart notebook

[codewithdaniel1]

Summary

Adds a general thermocycler quickstart notebook to address issue #633.

The notebook uses ThermocyclerChatterboxBackend so users can run the examples without physical hardware. It demonstrates:

• creating a Thermocycler
• opening and closing the lid
• setting block and lid temperatures
• querying temperature, lid, and status values
• running a custom Protocol
• running a PCR profile
• deactivating the block and lid

The thermocycling overview page now links to the new quickstart notebook.

Closes #633

Testing

Ran the notebook code locally as an async Python script using the real PyLabRobot classes:

• Thermocycler
• ThermocyclerChatterboxBackend
• Protocol
• Stage
• Step

Confirmed the example workflow runs successfully and prints the expected chatterbox output.

Also ran:

git diff --cached --check

Result: no output.