Add kubernetes backend options to build and test steps

Give the build/lint/test CI steps the same serviceAccount + resource
requests/limits as the pre-commit and release steps, so every step on the k8s
woodpecker backend is scheduled with bounded resources.

.woodpecker/build.yml

@@ -6,3 +6,13 @@ steps:
     image: golang:1.25
     commands:
       - make build
+    backend_options:
+      kubernetes:
+        serviceAccountName: default
+        resources:
+          requests:
+            memory: 512Mi
+            cpu: 1
+          limits:
+            memory: 2Gi
+            cpu: 2

.woodpecker/test.yml

@@ -6,8 +6,28 @@ steps:
     image: golang:1.25
     commands:
       - make lint
+    backend_options:
+      kubernetes:
+        serviceAccountName: default
+        resources:
+          requests:
+            memory: 512Mi
+            cpu: 1
+          limits:
+            memory: 2Gi
+            cpu: 2
 
   - name: test
     image: golang:1.25
     commands:
       - make test
+    backend_options:
+      kubernetes:
+        serviceAccountName: default
+        resources:
+          requests:
+            memory: 512Mi
+            cpu: 1
+          limits:
+            memory: 2Gi
+            cpu: 2