Fix copyright compliance in Frends.Pgp.SignFile csproj

[Copilot]

The <Copyright> tag in Frends.Pgp.SignFile.csproj didn't satisfy the platform compliance rule requiring <Copyright>Frends</Copyright>.

Changes

• Frends.Pgp.SignFile.csproj: Replace Copyright (c) 2026 Frends EiPaaS with Frends; bump version 1.2.0 → 1.3.0
• CHANGELOG.md: Add [1.3.0] entry

<!-- Before -->
<Copyright>Copyright (c) 2026 Frends EiPaaS</Copyright>

<!-- After -->
<Copyright>Frends</Copyright>

[jefim]

@copilot fix the build issues

[Copilot]

@copilot fix the build issues

Fixed in the latest commit. NUnit 4.6.1 (resolved by the 4.* wildcard) introduced an Action overload for Assert.Throws that conflicted with the existing TestDelegate overload, causing CS0121. Pinned NUnit to 4.3.2 and NUnit3TestAdapter to 5.0.0 (matching the EncryptFile project which already builds cleanly). The solution now builds without errors.

[jefim]

@copilot address review comments

[jefim]

No, leave the 4.* and 6.* versions, and fix the unit tests instead

[Copilot]

Reverted the version pin. Fixed the unit tests by casting each Assert.Throws lambda to (Action), which resolves the CS0121 ambiguity introduced in NUnit 4.6+ and uses the new preferred overload. Solution builds with 0 errors and 0 warnings.

[Copilot]

@copilot address review comments

Done — reverted the NUnit version pin and fixed the unit tests by casting the lambdas to (Action) instead.