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/repository/permission_provider.go

@@ -0,0 +1,38 @@
+package repository
+
+import (
+	"context"
+	"database/sql"
+	"errors"
+
+	"code.nochebuena.dev/go/rbac"
+	"code.nochebuena.dev/go/sqlite"
+)
+
+// DBPermissionProvider implements rbac.PermissionProvider by reading the
+// user_role table. A missing row is treated as "no permissions" (mask = 0).
+type DBPermissionProvider struct {
+	db sqlite.Client
+}
+
+// NewPermissionProvider returns a DBPermissionProvider backed by the given client.
+func NewPermissionProvider(db sqlite.Client) *DBPermissionProvider {
+	return &DBPermissionProvider{db: db}
+}
+
+// ResolveMask returns the permission bit-mask for uid on resource.
+// Returns 0 (no permissions) if no row exists for the user/resource pair.
+func (p *DBPermissionProvider) ResolveMask(ctx context.Context, uid, resource string) (rbac.PermissionMask, error) {
+	row := p.db.GetExecutor(ctx).QueryRowContext(ctx,
+		`SELECT permissions FROM user_role WHERE user_id = ? AND resource = ?`,
+		uid, resource,
+	)
+	var bits int64
+	if err := row.Scan(&bits); err != nil {
+		if errors.Is(err, sql.ErrNoRows) {
+			return 0, nil
+		}
+		return 0, err
+	}
+	return rbac.PermissionMask(bits), nil
+}