ci: run tests and CodeQL on k3s self-hosted amd64 runners

- ci-tests.yml: drop ubuntu/macos/windows matrix → single k3s amd64 runner
- ci-codeql-analysis.yml: ubuntu-latest → k3s amd64 runner
Fork targets amd64 cluster only; self-hosted runners have Docker for Testcontainers

.github/workflows/ci-codeql-analysis.yml

@@ -11,7 +11,7 @@ on:
 jobs:
   analyze:
     name: Analyze
-    runs-on: ubuntu-latest
+    runs-on: [self-hosted, k3s, linux, amd64]
 
     strategy:
       fail-fast: false

.github/workflows/ci-tests.yml

@@ -13,12 +13,7 @@ env:
 
 jobs:
   run-tests:
-    strategy:
-      matrix:
-        os: ["ubuntu-latest", "macos-latest", "windows-latest"]
-      fail-fast: false
-
-    runs-on: "${{ matrix.os }}"
+    runs-on: [self-hosted, k3s, linux, amd64]
     steps:
       - uses: actions/checkout@8e8c483db84b4bee98b60c0593521ed34d9990e8 # v6.0.1