feat(todo-api): add full-stack POC demonstrating micro-lib v0.9.0

Runnable REST API exercising every micro-lib tier in a containerless setup: N-layer architecture, SQLite persistence, header-based auth simulating Firebase output, and bit-mask RBAC enforcement.

What's included:
- cmd/todo-api: minimal main delegating to application.Run
- internal/application: full object graph wiring — launcher, sqlite, httpserver, httpmw stack, routes in BeforeStart
- internal/domain: User entity, ResourceTodos constant, PermReadTodo/PermWriteTodo bit positions
- internal/repository: TodoRepository, UserRepository, DBPermissionProvider (SQLite via modernc)
- internal/service: TodoService, UserService with interface-based dependencies
- internal/handler: TodoHandler, UserHandler using httputil adapters and valid for input validation
- internal/middleware: Auth (X-User-ID → rbac.Identity) and Require (bit-mask permission gate)
- logAdapter: bridges logz.Logger.With return type to httpmw.Logger interface
- SQLite schema: users, user_role (bitmask), todos; migrations run in BeforeStart
- Routes: POST /users (open), GET+POST /todos (RBAC), GET /users (RBAC)

Tested-via: todo-api POC integration
Reviewed-against: docs/adr/

internal/service/todo_service.go

@@ -0,0 +1,36 @@
+package service
+
+import (
+	"context"
+
+	"code.nochebuena.dev/go/todo-api/internal/domain"
+	"code.nochebuena.dev/go/todo-api/internal/repository"
+)
+
+// CreateTodoRequest is the input for creating a new todo.
+type CreateTodoRequest struct {
+	Title string `json:"title" validate:"required,min=1,max=255"`
+}
+
+// TodoService handles todo business logic.
+type TodoService interface {
+	FindAll(ctx context.Context) ([]domain.Todo, error)
+	Create(ctx context.Context, req CreateTodoRequest) (domain.Todo, error)
+}
+
+type todoService struct {
+	repo repository.TodoRepository
+}
+
+// NewTodoService returns a TodoService backed by the given repository.
+func NewTodoService(repo repository.TodoRepository) TodoService {
+	return &todoService{repo: repo}
+}
+
+func (s *todoService) FindAll(ctx context.Context) ([]domain.Todo, error) {
+	return s.repo.FindAll(ctx)
+}
+
+func (s *todoService) Create(ctx context.Context, req CreateTodoRequest) (domain.Todo, error) {
+	return s.repo.Create(ctx, domain.Todo{Title: req.Title})
+}