perf(desktop): preload auth before the first Compose frame

[ThePunpun]

Summary

Initialize cached authentication in the Desktop entry point before the first Compose frame, alongside the existing cached-profile preload.

This is the exact Desktop-only Main.kt portion of the original implementation in NuvioDesktop PR #546, rebased onto the latest Dev. The four shared commonMain changes are intentionally submitted through companion NuvioMobile PR #1854.

PR type

• Reproducible bug fix
• UI glitch/bug fix
• Behavior bug/regression fix
• Small maintenance only, with no UI or behavior change
• Docs accuracy fix
• Translation/localization only
• Approved larger or directional change

Why

Desktop already restores cached profiles synchronously before creating the Compose window, but cached authentication was initialized later from the shared app gate.

Preloading authentication beside the profile cache gives the first frame the complete restored startup state and avoids an unnecessary startup-state transition. The later shared initialization remains safe because AuthRepository.initialize() is idempotent.

Desktop scope

This changes only the shared Desktop entry point used by Windows, macOS, and Linux.

It does not modify commonMain or native Mobile entry points. The related shared startup behavior is isolated in NuvioMobile PR #1854, following the maintainer direction recorded in NuvioDesktop PR #546.

Issue or approval

Fixes #580

Original implementation and visual context: NuvioDesktop PR #546

Companion shared change: NuvioMobile PR #1854

UI / behavior impact

• No UI change
• No behavior change
• UI changed only to fix a documented glitch/bug
• Behavior changed only to fix a documented bug/regression
• UI change has explicit maintainer approval
• Behavior change has explicit maintainer approval

Policy check

• I have read and understood CONTRIBUTING.md.
• This PR is small, focused, and limited to one problem.
• This PR is scoped to the desktop app, desktop packaging, desktop documentation, or shared code required for desktop behavior.
• This PR is not cosmetic-only.
• Any UI change fixes a linked glitch/bug and includes visual proof, or this PR has no UI change.
• Any behavior change fixes a linked bug/regression or has explicit approval, or this PR has no behavior change.
• This PR does not bundle unrelated refactors, cleanups, formatting, or drive-by changes.
• This PR does not add dependencies, architecture changes, migrations, or product-direction changes without explicit approval.
• I listed the testing performed below.

Scope boundaries

Only composeApp/src/desktopMain/kotlin/com/nuvio/app/Main.kt was changed.

No shared startup flow, UI implementation, dependencies, architecture, profile behavior, networking, or unrelated Desktop initialization was changed in this PR.

The newer startup-performance work already present in Dev, including commit 82310de4, is preserved.

Testing

• Ran .\gradlew.bat --offline --console=plain :composeApp:compileKotlinDesktop.
• Launched the Desktop app from the updated branch on Windows 11 with an existing signed-in account and cached profile.
• Confirmed the app reached Home normally, remained responsive, and showed no regression from the preload ordering change.
• macOS and Linux runtime behavior was not manually verified.

Screenshots / Video

Not a UI change.

The complete combined startup result and original before/after recordings are available in NuvioDesktop PR #546. Its four shared commonMain files are now represented by companion NuvioMobile PR #1854.

Breaking changes

None.

Linked issues

Fixes #580

Companion shared change: NuvioMobile PR #1854