feature: basic scrollbar support for tables and dialogs

[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:

Adds scrollbars to dialogs (help, process kill) and optionally tables.

Table:

Dialogs:

Example with another theme:

Issue

If applicable, what issue does this address?

Closes: #1555

Testing

If relevant, please state how this was tested (including steps):

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 24.24242% with 75 lines in your changes missing coverage. Please review.
✅ Project coverage is 62.04%. Comparing base (5d09d18) to head (b089b69).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
src/canvas/dialogs/help_dialog.rs	0.00%	25 Missing ⚠️
src/canvas/components/scroll_bar.rs	0.00%	20 Missing ⚠️
src/canvas/components/data_table/draw.rs	33.33%	18 Missing ⚠️
src/canvas/dialogs/process_kill_dialog.rs	0.00%	12 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2046      +/-   ##
==========================================
+ Coverage   55.87%   62.04%   +6.17%     
==========================================
  Files         124      125       +1     
  Lines       17580    17669      +89     
==========================================
+ Hits         9822    10963    +1141     
+ Misses       7758     6706    -1052     

Flag	Coverage Δ
macos-14	49.01% <15.15%> (-0.19%)	⬇️
ubuntu-24.04	60.93% <24.24%> (+6.47%)	⬆️
windows-2022	48.70% <17.24%> (-0.15%)	⬇️

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