refactor: remove battery conversion step

[ClementTsang]

Description

A description of the change, what it does, and why it was made. If relevant (such as any change that modifies the UI), please provide screenshots of the changes:

Simplify some of the data-to-display pipeline for battery data; also fix some width bugs.

Issue

If applicable, what issue does this address?

Closes: #

Testing

If relevant, please state how this was tested. All changes must be tested to work:

If this is a code change, please also indicate which platforms were tested:

• Windows
• macOS
• Linux

Checklist

If relevant, ensure the following have been met:

• Areas your change affects have been linted using rustfmt (cargo fmt)
• The change has been tested and doesn't appear to cause any unintended breakage
• Documentation has been added/updated if needed (README.md, help menu, doc pages, etc.)
• The pull request passes the provided CI pipeline
• There are no merge conflicts
• If relevant, new tests were added (don't worry too much about coverage)

[codecov]

Codecov Report

Attention: Patch coverage is 6.49351% with 72 lines in your changes missing coverage. Please review.

Project coverage is 41.27%. Comparing base (603d8fe) to head (0eccf25).
Report is 3 commits behind head on main.

Files with missing lines	Patch %	Lines
src/data_collection/batteries.rs	0.00%	41 Missing ⚠️
src/canvas/widgets/battery_display.rs	9.67%	28 Missing ⚠️
src/app/data_farmer.rs	0.00%	1 Missing ⚠️
src/canvas/components/data_table/draw.rs	0.00%	1 Missing ⚠️
src/lib.rs	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1652      +/-   ##
==========================================
- Coverage   41.28%   41.27%   -0.01%     
==========================================
  Files         108      108              
  Lines       17898    17893       -5     
==========================================
- Hits         7389     7386       -3     
+ Misses      10509    10507       -2     

Flag	Coverage Δ
macos-14	37.28% <6.49%> (+0.01%)	⬆️
ubuntu-latest	42.99% <6.49%> (-0.01%)	⬇️
windows-2019	37.21% <6.49%> (+0.01%)	⬆️

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