feat: Add budget balance and filter for budget in get_transactions

[bvanelli]

Allows you to check the balance for your budget, as well as retrieve the transactions for each budget.

I did try to create transactions directly as a budget property, but that runs into different issues:

• Creating the relationship is quite hard since we have to compare an integer from the budget in the form 202410, with an integer in the transactions table in the form 20241005. This makes the "safe" relationship harder to achieve. - When using instead a property, the sqlalchemy session is used instead of the sqlmodel session. It's probably not safe either since we have to convert the result first to the correct models, and I don't know if they would work 100%.

I instead included the budget filter in the get_transactions instead.
For example:

...
budget = get_budget(actual.session, datetime.date.today(), "Food")
print(f"Available to spend is: {budget.get_amount()}")
print(f"Already spent is: {budget.balance}")

For me prints:

Available to spend is: 30
Already spent is: -35

And frontend shows:

Closes #90

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 97.69%. Comparing base (2c89c52) to head (475beef).
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #91      +/-   ##
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+ Coverage   97.67%   97.69%   +0.01%     
==========================================
  Files          16       16              
  Lines        2196     2213      +17     
==========================================
+ Hits         2145     2162      +17     
  Misses         51       51              

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[raiyni]

This seems good with my testing