feature: add disk usage chart widget

[ClementTsang]

Description

A description of the change, what it does, and why it was made. If relevant (e.g. UI changes), please also provide screenshots/recordings:

Issue

If applicable, what issue does this address?

Closes: #205

Testing

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If this change affects the program, please also indicate which platforms were tested:

• Windows
• macOS (specify version below)
• Linux (specify distro below)
• Other (specify below)

Checklist

Ensure all of these are met:

• If this PR adds or changes a dependency, please justify this in the description
• If this is a code change, areas your change affects have been linted using (cargo fmt)
• If this is a code change, your changes pass cargo clippy --all -- -D warnings
• If this is a code change, new tests were added if relevant
• If this is a code change, your changes pass cargo test
• The change has been tested to work (see above) and doesn't appear to break other things
• Documentation has been updated if needed (README.md, help menu, docs, configs, etc.)
• There are no merge conflicts
• You have reviewed your changes first
• The pull request passes the provided CI pipeline

Other

Anything else that maintainers should know about this PR:

[codecov]

Codecov Report

❌ Patch coverage is 25.17730% with 211 lines in your changes missing coverage. Please review.
✅ Project coverage is 61.27%. Comparing base (fca070e) to head (c5dcf42).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
src/canvas/widgets/disk_space_graph.rs	0.00%	79 Missing ⚠️
src/app/data/time_series.rs	0.00%	46 Missing ⚠️
src/canvas/widgets/mod.rs	0.00%	22 Missing ⚠️
src/canvas/widgets/disk_io_graph.rs	0.00%	13 Missing ⚠️
src/options.rs	67.50%	13 Missing ⚠️
src/canvas.rs	0.00%	11 Missing ⚠️
src/widgets/disk_space_graph.rs	0.00%	8 Missing ⚠️
src/app/states.rs	37.50%	5 Missing ⚠️
src/options/config/disk_io_graph.rs	0.00%	5 Missing ⚠️
src/app/data/store.rs	69.23%	4 Missing ⚠️
... and 3 more

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2081      +/-   ##
==========================================
- Coverage   61.82%   61.27%   -0.55%     
==========================================
  Files         132      135       +3     
  Lines       19123    19271     +148     
==========================================
- Hits        11822    11808      -14     
- Misses       7301     7463     +162     

Flag	Coverage Δ
macos-14	49.21% <21.14%> (-0.34%)	⬇️
ubuntu-24.04	60.23% <25.08%> (-0.56%)	⬇️
windows-2022	48.93% <21.27%> (-0.35%)	⬇️

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