GHA/checksrc: run reuse directly, merge into the linters workflow

To eliminate dependencies on an Action, Docker Hub and to simplify.

Closes #18721

.github/scripts/requirements.txt

@@ -5,4 +5,5 @@
 cmakelang == 0.6.13
 codespell == 2.4.1
 pytype == 2024.10.11
+reuse == 5.1.1
 ruff == 0.13.1

.github/workflows/checksrc.yml

@@ -43,8 +43,8 @@ jobs:
       - name: 'check'
         run: scripts/checksrc-all.pl
 
-  spellcheck-cmakelint-pytype-ruff:
-    name: 'spellcheck, cmakelint, pytype, ruff'
+  linters:
+    name: 'spellcheck, linters, REUSE'
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@08c6903cd8c0fde910a37f88322edcfb5dd907a8 # v5
@@ -61,6 +61,11 @@ jobs:
             -r tests/http/requirements.txt \
             -r tests/requirements.txt
 
+      - name: 'REUSE check'
+        run: |
+          source ~/venv/bin/activate
+          reuse lint
+
       - name: 'codespell'
         run: |
           source ~/venv/bin/activate
@@ -89,17 +94,6 @@ jobs:
           source ~/venv/bin/activate
           scripts/pythonlint.sh
 
-  reuse:
-    name: 'REUSE'
-    runs-on: ubuntu-latest
-    steps:
-      - uses: actions/checkout@08c6903cd8c0fde910a37f88322edcfb5dd907a8 # v5
-        with:
-          persist-credentials: false
-
-      - name: 'check'
-        uses: fsfe/reuse-action@bb774aa972c2a89ff34781233d275075cbddf542 # v5
-
   complexity:
     name: 'complexity'
     runs-on: ubuntu-latest