[DEV-75] Declutter starting screen and simplify first-time project setup

[danii1]

Task: DEV-75

Summary: Declutter starting screen and simplify first-time project setup

Implementation Details

Implemented DEV-75.

• Added a dedicated launch state with exactly one loading spinner.
• Hidden actions and recent projects while automatically opening a project.
• Removed disabled “Open existing folder” states—the control is either actionable or absent.
• Simplified first-project guidance and removed the empty recent-projects box.
• Recent projects now render only when entries exist.
• Added focused regression tests in SetupEmptyState.test.tsx.

Implementation: SetupEmptyState.tsx

Validation:

• 10 focused tests pass.
• Formatting passes.
• Lint passes with pre-existing warnings.
• Full suite reached 467 passing tests; one existing test and typecheck are blocked because dompurify is missing from installed modules despite being present in package.json and bun.lock. The sandbox also prevented Bun from restoring dependencies.

---

This PR was automatically created by @devintern/code

[danii1]

@devintern-internal bump pm-desktop version(patch), we'll release this