ci: pin setup-uv to v8.1.0 (no moving v8 tag exists)

astral-sh/setup-uv publishes moving major tags only through v7; v8 exists
only as exact releases, so @v8 fails to resolve. Pin to v8.1.0.

Generated with [Claude Code](https://claude.ai/code)
via [Happy](https://happy.engineering)

Co-Authored-By: Claude <noreply@anthropic.com>
Co-Authored-By: Happy <yesreply@happy.engineering>

Author: 3 people

.github/workflows/ci.yml

@@ -45,7 +45,7 @@ jobs:
         uses: actions/checkout@v6
 
       - name: Set up uv
-        uses: astral-sh/setup-uv@v8
+        uses: astral-sh/setup-uv@v8.1.0
         with:
           version: "latest"
           enable-cache: true
@@ -86,7 +86,7 @@ jobs:
         uses: actions/checkout@v6
 
       - name: Set up uv
-        uses: astral-sh/setup-uv@v8
+        uses: astral-sh/setup-uv@v8.1.0
         with:
           version: "latest"
           enable-cache: true

src/quickforge/templates/github_ci.yml.j2

@@ -46,7 +46,7 @@ jobs:
         uses: actions/checkout@v6
 
       - name: Set up uv
-        uses: astral-sh/setup-uv@v8
+        uses: astral-sh/setup-uv@v8.1.0
         with:
           version: "latest"
           enable-cache: true
@@ -91,7 +91,7 @@ jobs:
         uses: actions/checkout@v6
 
       - name: Set up uv
-        uses: astral-sh/setup-uv@v8
+        uses: astral-sh/setup-uv@v8.1.0
         with:
           version: "latest"
           enable-cache: true