Fix note list rendering at fractional display scaling

[Shriram-Vasudevan]

Summary

• set Qt high-DPI scale factor rounding to pass through before creating the application
• create note-list delegate paint buffers with the owning widget/window device-pixel ratio
• use logical buffer geometry while painting cropped row backgrounds/labels, so Windows fractional scaling does not mix physical pixmap pixels with logical item rects

Fixes #164.

Verification

• git diff --check
• c++ -std=c++17 -fsyntax-only -include arm_acle.h ... src/notelistdelegate.cpp src/notelistdelegateeditor.cpp against locally installed Qt 6.9.2 headers
• syntax-only check for QGuiApplication::setHighDpiScaleFactorRoundingPolicy(...) against Qt 6.9.2 headers

I could not run the full CMake build locally because cmake is not installed in this environment, and clang-format is also unavailable locally.

[zjeffer]

@nuttyartist Do we have an AI-policy? Personally I'm not a big fan of these fully AI-generated PRs, I mean the OP didn't even bother to let the AI install cmake:

I could not run the full CMake build locally because cmake is not installed in this environment, and clang-format is also unavailable locally.

I recently added one in a personal repo if you want an example: https://github.com/zjeffer/split-monitor-workspaces/blob/main/CONTRIBUTING.md

[Shriram-Vasudevan]

I installed the missing local build tooling and pushed follow-up commit 404e7cf with the clang-format adjustments found by the repo format gate.

Verification now run locally:

• /opt/homebrew/opt/llvm/bin/clang-format -style=file --dry-run --Werror --color=false src/main.cpp src/notelistdelegate.cpp src/notelistdelegateeditor.cpp src/utils.h -> passed
• find src/ -iregex '.*\.\(cpp\|h\|mm\)$' -print0 | xargs -n 1 -0 /opt/homebrew/opt/llvm/bin/clang-format -style=file --dry-run --Werror --color=false -> passed
• cmake . --warn-uninitialized --warn-unused-vars -G Ninja -B build -DCMAKE_BUILD_TYPE=debug -DCMAKE_PREFIX_PATH="$(brew --prefix qt@6)" -DPRO_VERSION=OFF -> passed with Qt 6.9.2
• cmake --build build -> passed
• ctest --test-dir build --output-on-failure -> no tests registered
• git diff --check -> passed

The build produced only existing/project-wide Qt deprecation and macOS deployment-target linker warnings, not errors in the touched note-list files.