chore: Various improvements and fixes

[letehaha]

• [x] improve system amount calculations. Move system amount handling into the API layer for response
• [x] fix dropdown crashing
• [x] fix Expenses Structure internal calculation
• [x] move vue-query cache keys to a single place

[cypress[bot]]

Passing run #230 ↗︎

0	12	0	0	0
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Details:

Merge 7cb8ff05199dbf7ea0140ddedd929a8170971d14 into e039b8ea240f7c3873378a6d1649...
Project: budget-tracker	Commit: 95c67821f2 ℹ️
Status: Passed	Duration: 02:05 💡
Started: Aug 31, 2023 7:31 PM	Ended: Aug 31, 2023 7:33 PM

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