[Bug]: The copyright year differs between the csproj and the .nuspec

### Description

The generated package declares two different copyright years:

* `templates/Source/MyPackage/MyPackage.csproj` uses `Copyright 2026-$([System.DateTime]::Now.ToString(yyyy)) Your Name`
* `templates/Source/MyPackage/nuspec` hardcodes `Copyright 2025 Your Name`

So a binary package and a source-only package generated on the same day claim different years, and the nuspec value never updates.

### Expected behavior

Both files use the same placeholder, and the year is either derived at build time or is an obvious placeholder the user is told to replace.

### Actual behavior

The nuspec is stuck at 2025 and disagrees with the csproj.

### Other information

The csproj value hardcodes `2026` as the start year, which is also wrong for anyone generating a project later. A plain placeholder such as `Copyright (c) YEAR Your Name`, called out in the "what to do next" list in the generated README, may be simpler than trying to be clever with MSBuild functions.

Compare templates/Source/MyPackage/MyPackage.csproj with templates/Source/MyPackage/nuspec, then inspect the generated README's "what to do next" list. Make the copyright handling consistent in both generated files and ensure the README explains any placeholder users must replace; verify that generated packages no longer claim different years.

Written by the indexing model from the issue text.