🧪 [testing improvement] Add unit tests for init_economy in quickstart.py

[mapleleaflatte03]

🎯 What: The testing gap addressed
This PR introduces unit tests for the init_economy function in quickstart.py. It creates a new test file test_quickstart.py in the root directory.

📊 Coverage: What scenarios are now tested

1. Ledger file already exists (it should skip file creation).
2. Neither ledger file nor revenue file exists (it should create both with default economy setup).
3. Ledger file is missing but revenue file exists (it should only create the ledger file).

✨ Result: The improvement in test coverage
The code for initializing the basic economy data structure is now covered. This gives safety moving forward when editing quickstart.py.

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PR created automatically by Jules for task 15829618859872487278 started by @mapleleaflatte03

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[mapleleaflatte03]

This repository is now archived for historical reference.\n\nActive Meridian development has moved to the monorepo:\nhttps://github.com/mapleleaflatte03/meridian\n\nPlease open a new PR against the monorepo if this change is still needed.