chore: synchronize version references to 3.0.0 across app and documentation

[Ivorisnoob]

Summary

Updated all legacy version references (2.0/2.0.0) to match the current release version (3.0.0). This ensures consistency between the codebase, internal fallback logic, and public-facing documentation.

Key Changes

• Documentation Updates: Refreshed the main project documentation and contributor guidelines to reflect the 3.0 release.
• UI & Display: Corrected version fallback strings used in the settings and main interface components.
• Internal Logic: Updated the version baselines used during the initial sync handshake and Mac compatibility checks to prevent version mismatch warnings.

Rationale

While the core build configuration was already set to 3.0.0, several hardcoded strings remained at 2.0.0. These changes ensure a unified versioning experience throughout the application and its documentation.

Verification

• Confirmed all identified legacy version strings have been updated to 3.0.0.
• Verified that these changes only affect string constants and do not impact core functionality.

[sameerasw]

Thank you for the contributions <3