Refactor the service layer

[BytecodeBrewer]

What changed?

• dissolve calculator and conversion service
• update exchange clients test

Related issue

Closes #71

Tests

• I ran pytest
• Existing tests pass
• I added or updated tests where necessary
• Not needed because this only affects documentation or repository setup

Checklist

• The change is focused
• No secrets or API keys are included
• Documentation was updated if needed
• CI is expected to pass

Notes

• methods from previosly conversion service aren't tested yet -> before the sprint 3 starts and CD Pipleline is going o be implemented, its need to be done.

[chatgpt-codex-connector]

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[chatgpt-codex-connector]

Populate the trend request with usable FX metadata

When the Trend Chart is opened on a fresh database, this request is the only thing used by prepare_trend_analysis. read_price_bars searches by source.name and instrument.symbol, so name="" won't match rows inserted under real sources, and on a miss yfinance_client.get_timeseries constructs its ticker from instrument.base_currency and quote_currency, both left as None here. The result is a NoneNone=X lookup and no chart for EUR/USD instead of fetching/caching the intended pair.

Useful? React with 👍 / 👎.

[chatgpt-codex-connector]

Restore the API lookup for legacy conversions

After interface.py was switched to import legacy.services.conversion_service, every legacy CLI conversion reaches this get_conv_rate. This unconditional branch returns None for all currency pairs, so display_convert never succeeds and stays in the retry loop even for valid inputs that used to call exchangerate_client.get_rates. Please keep the real rate lookup when moving the service.

Useful? React with 👍 / 👎.