fix(windows): restore popup and quota runtime access

[MarsSall]

Closes #30

PR type

• Bug fix
• New feature
• Documentation only
• Code refactoring
• Maintenance/tooling
• Breaking change

Summary

• Restore WPF popup rendering when startup created the native handle while hidden.
• Export privacy-safe unavailable/diagnostic states instead of leaving enabled failures as disabled.
• Keep the shared Windows data directory accessible to sibling SQLite stores while restricting ACLs to the current user and LocalSystem.

Changes

File	Change
src/AIBar.Desktop/WindowsTheme.cs	Avoid the invalid post-handle AllowsTransparency assignment.
src/AIBar.Application/QuotaExport.cs	Publish unavailable after a completed enabled attempt without a snapshot.
src/AIBar.Desktop/QuotaPresentation.cs	Map quota failures through a closed sanitized diagnostic allowlist.
src/AIBar.Application/LocalCodexAnalytics.cs	Classify local analytics failures by safe processing stage.
src/AIBar.Desktop/LocalCodexAnalyticsView.cs	Publish classified failures without exposing exception details.
src/AIBar.Desktop/QuotaExportWindows.cs	Use protected inheritable current-user/LocalSystem directory ACLs while preserving the narrower snapshot ACL.
tests/AIBar.Domain.Tests/*	Cover popup handle creation, export state transitions, diagnostic containment, lifecycle failures, and sibling ACL behavior.

Test plan

• Full domain suite: dotnet test tests/AIBar.Domain.Tests/AIBar.Domain.Tests.csproj -c Release --no-restore — 592 passed, 0 failed.
• Focused popup/quota/ACL regression set — 71 passed, 0 failed.
• Release Windows build: dotnet build src/AIBar.Desktop/AIBar.Desktop.csproj -c Release -r win-x64 --no-restore — 0 warnings, 0 errors.
• Manual Windows verification: popup opens, databases retain access after restart, and YASB reaches sanitized state=current.
• Shellcheck not applicable: no shell scripts changed.

Contributor checklist

• Linked approved issue fix: restore Windows popup and quota runtime access #30.
• Added exactly one type:* label.
• Tests are included with each behavior change.
• No documentation update is required for this corrective runtime behavior.
• Conventional commit format used.
• No AI attribution or Co-Authored-By trailers.