BTC 2025 Daily Simulation

[jribbink]

Create a forked mainnet simulation using real daily BTC prices for 2025.

• Pull ~1 year of daily BTC/USD prices (e.g. from CoinMarketCap or similar)
• Generate a fixture file for the test (see flash_crash_moderate_helpers.cdc for rough format)
• Write the simulation test — daily rebalances, check health factors, etc. (see forked_flash_crash_moderate_test.cdc as a rough starting point)

The existing flash crash test and scripts/generate_fixture.py are rough/exploratory - feel free to restructure as needed.

Reference: BTC flash crash POC/draft branch https://github.com/onflow/FlowYieldVaults/blob/jribbink/time-series-sim/cadence/tests/forked_flash_crash_moderate_test.cdc