Backport selected upstream reliability fixes to Classic

[martesi]

Summary

Carries the existing Classic patch-stack/release work and six selected upstream reliability backports onto main, while preserving Classic-specific guards and WinUI behavior.

Included upstream backports

• #5312: column-aware Cargo package-list parsing.
• #4974: cleanup of orphaned manager listing processes on timeout.
• #5321: resilient Scoop listing process handling.
• #5322: manager dependency verification and Cargo binary detection.
• #5309: PowerShell 5 module-operation failure propagation.
• #5244: Pinget no-applicable-upgrade detection.

Upstream commit and PR provenance is recorded in maintenance/backports.yml.

Classic-specific decisions

• The upstream Avalonia-only dialog rewrite from Verify manager dependency installations and detect cargo dependencies Devolutions/UniGetUI#5322 is intentionally excluded; equivalent dependency-install verification was adapted to Classic WinUI.
• The Handle Pinget no-applicable upgrade result with zero exit code Devolutions/UniGetUI#5244 change preserves Classic's existing retry and phantom-update guards.
• The timeout/process cleanup from [BUG] Large CPU usage after UniGetUI has been running a few hours Devolutions/UniGetUI#4974 was adapted to Classic's manager infrastructure and used as the prerequisite for Keep Scoop package listings working when scoop commands fail Devolutions/UniGetUI#5321.
• Existing patch-stack and release commits on this branch are retained.

Validation

• Passed clean-worktree and whitespace checks.
• Passed JSON validation and merge-marker checks.
• Confirmed Classic patch-stack guard files are unchanged.
• .NET tests were not run because the active environment lacks dotnet/PowerShell tooling and Windows interop is unavailable.

This is a selective backport; remaining upstream UI/Avalonia, workflow, translation, and unrelated changes are intentionally outside this PR.