feat: scoped multi-namespace mode (Role per namespace, no ClusterRole)

Add a third RBAC posture between watch-globally (ClusterRole) and single
namespace: give Reloader an explicit list of namespaces to watch. The chart
creates a namespace-scoped Role + RoleBinding in each listed namespace (no
ClusterRole), and one install covers them all.

Go:
- new --namespaces flag / options.Namespaces
- resolveWatchNamespaces() picks list -> KUBERNETES_NAMESPACE -> all
- controller creation loops over the watched namespaces
- namespaces-to-ignore is now only honored in global mode (watchGlobally=true);
  in single-namespace and scoped modes the watched set is already explicit

Helm:
- new reloader.namespaces value (active when watchGlobally=false); accepts either
  a YAML list or a comma-separated string for consistency with the sibling
  namespace options
- reloader-watchNamespaces helper (release ns always auto-included, deduped)
- shared reloader-namespaced-rules template reused per namespace
- role.yaml/rolebinding.yaml range over the list; deployment passes --namespaces
- --namespaces-to-ignore only rendered when watchGlobally=true
- fail guard for watchGlobally=true + namespaces set

Tests: unit test for resolveWatchNamespaces; scoped-namespaces e2e case.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

internal/pkg/options/flags.go

@@ -76,6 +76,9 @@ var (
 	ResourcesToIgnore = []string{}
 	// WorkloadTypesToIgnore is a list of workload types to ignore when watching for changes
 	WorkloadTypesToIgnore = []string{}
+	// Namespaces is an explicit list of namespaces to watch (scoped mode). When non-empty,
+	// Reloader watches exactly these namespaces and requires no ClusterRole.
+	Namespaces = []string{}
 	// NamespacesToIgnore is a list of namespace names to ignore when watching for changes
 	NamespacesToIgnore = []string{}
 	// NamespaceSelectors is a list of namespace selectors to watch for changes