fix(settings): keep controls reachable on small displays

[laceyp99]

Summary

Fixes #31 by making every Settings tab vertically scrollable and fitting the window to the opening monitor's usable work area on constrained displays. The existing 760x700 default is retained where it fits. Windows tab scrolling now moves 60 pixels per wheel notch while slider value scrolling remains unchanged. Scrollable surfaces use matching light/dark colors.

Validation

• venv\Scripts\python.exe -m ruff format --check .
• venv\Scripts\python.exe -m ruff check .
• venv\Scripts\python.exe -m pytest (167 passed)
• Real-widget checks: default sizing, work-area sizing, 60-pixel wheel travel, slider isolation
• Human verification: current display and 1366x768 at 100% and 150%; all tab controls reachable, no clipping, faster scrolling, reset isolation, Cancel/Save persistence, light/dark appearance

Notes

Ollama connection testing and secondary-monitor placement were not exercised. docs/plan.md and review.md remain local untracked artifacts.

[laceyp99]

Looks good to me. I was part of the interactive UI testing making sure in different display setups and everything mainly looked good. I'm glad I was able to catch the slow vertical scrolling and dark/light mode visibility support.

[laceyp99]

Did a quick second monitor test and nothing was caught as far as issues/bugs. Ollama is left untested as it isn't relevant to this patch.