refactor(10.2-01): nest framework packages under modules

- Move remaining beach packages and embedded admin assets\n- Rewrite framework, example, build, and gate paths

modules/backpack/services.go

@@ -0,0 +1,60 @@
+package backpack
+
+import (
+	"fmt"
+	"reflect"
+	"sync"
+)
+
+// Registry is an app-scoped typed service catalog. It has no process-global state.
+type Registry struct {
+	mu sync.RWMutex
+	m  map[reflect.Type]any
+}
+
+// NewRegistry returns an empty service registry.
+func NewRegistry() *Registry {
+	return &Registry{m: make(map[reflect.Type]any)}
+}
+
+// Publish stores value under the concrete type argument T. Publishing the
+// same T twice is an error.
+func (r *Registry) Publish[T any](value T) error {
+	if r == nil {
+		return fmt.Errorf("backpack: registry is nil")
+	}
+	if any(value) == nil {
+		return fmt.Errorf("backpack: publish nil service")
+	}
+	key := reflect.TypeFor[T]()
+	r.mu.Lock()
+	defer r.mu.Unlock()
+	if r.m == nil {
+		r.m = make(map[reflect.Type]any)
+	}
+	if _, exists := r.m[key]; exists {
+		return fmt.Errorf("backpack: duplicate provider for %s", key)
+	}
+	r.m[key] = value
+	return nil
+}
+
+// Lookup returns the service published under T, or (zero, false).
+func (r *Registry) Lookup[T any]() (T, bool) {
+	var zero T
+	if r == nil {
+		return zero, false
+	}
+	key := reflect.TypeFor[T]()
+	r.mu.RLock()
+	defer r.mu.RUnlock()
+	v, ok := r.m[key]
+	if !ok {
+		return zero, false
+	}
+	got, ok := v.(T)
+	if !ok {
+		return zero, false
+	}
+	return got, true
+}