feat(opa): add conftest OPA policies and pre-commit hook

Adds three policy files under policy/ plus a pre-commit hook that
runs conftest against all staged YAML manifests (excluding chart
templates).

Policies:
  no_ingress.rego
    Deny Ingress resources — cluster uses Gateway API only.

  gateway_api.rego
    HTTPRoute/TLSRoute: require explicit group/kind on parentRefs and
    group/kind/weight on backendRefs (PR #162, #165).
    Gateway: require explicit group on certificateRefs (PR #153).
    All fields are defaulted by the controller; omitting them causes
    permanent ArgoCD OutOfSync.

  resource_normalization.rego
    CPU integer: deny unquoted integer cpu values (PR #163).
    CPU milliCPU: deny values like 1000m/2000m that normalise to "1"/"2" (PR #164).
    Memory Mi→Gi: deny 1024Mi/2048Mi etc. that normalise to 1Gi/2Gi (PR #163).
    clusterIP null: deny Service with explicit null clusterIP (PR #166).

Also fixes all existing violations found by the new policies across
puppet deployments and reposync cronjobs (resource normalization).
kanidm/tlsroute.yaml and puppet/service_puppetdb.yaml are excluded
from this commit as they are addressed in PRs #165 and #166.

apps/base/puppet/deployment_puppetboard.yaml

@@ -150,7 +150,7 @@ spec:
               memory: 350Mi
               cpu: 100m
             limits:
-              memory: 1024Mi
+              memory: 1Gi
               cpu: 500m
           securityContext:
             runAsNonRoot: true

apps/base/puppet/deployment_puppetdb.yaml

@@ -35,7 +35,7 @@ spec:
           imagePullPolicy: IfNotPresent
           resources:
             limits:
-              cpu: 1
+              cpu: "1"
               memory: 1536Mi
             requests:
               cpu: 250m

apps/base/puppet/deployment_puppetserver-compiler.yaml

@@ -31,11 +31,11 @@ spec:
         imagePullPolicy: IfNotPresent
         resources:
           limits:
-            cpu: 2
-            memory: 3072Mi
+            cpu: "2"
+            memory: 3Gi
           requests:
             cpu: 500m
-            memory: 1024Mi
+            memory: 1Gi
         ports:
         - containerPort: 8140
           name: puppetserver

apps/base/puppet/deployment_puppetserver-master.yaml

@@ -35,11 +35,11 @@ spec:
           imagePullPolicy: IfNotPresent
           resources:
             limits:
-              cpu: 2
+              cpu: "2"
               memory: 3500Mi
             requests:
               cpu: 250m
-              memory: 1024Mi
+              memory: 1Gi
           ports:
             - containerPort: 8140
               name: puppetserver