Unify TUnit version pinning strategy across templates

[thomhurst]

Problem

Template project files use inconsistent version strategies for TUnit package references:

Template	Strategy
TUnit (basic)	1.* wildcard
TUnit.AspNet	Pinned exact
TUnit.FSharp	Pinned exact
TUnit.AspNet.FSharp	Pinned exact
TUnit.VB	Pinned exact
TUnit.Playwright	Pinned exact

The basic TUnit template always scaffolds with the latest published version automatically. Every other template requires a Renovate PR to stay current, and freshly-scaffolded projects reference a stale version until that PR merges.

Suggested Fix

Align all templates on one strategy. Options:

1. 1.* wildcard everywhere — zero maintenance, users always get latest minor.
2. [1,2) floating range — NuGet-semver-safe, same effect without wildcard caveats.
3. Pinned exact everywhere — requires template TUnit to also be pinned and bumped by Renovate.

Option 1 or 2 eliminates this class of maintenance PR for template projects entirely.

Context

Surfaced in the code review on PR #5701. Related to #5708 (stale TUnit.Aspire in templates).