fix: set authenticated user on request context in bearer token auth

tryBearerAuth validated the bearer token but never looked up the
associated user or set it on the request context. This meant
downstream handlers calling GetCurrentUser would get nil even
with a valid token.

Changes:
- Add ContextWithUser/UserFromContext helpers in auth package
- tryBearerAuth now looks up the user by token's UserID and
  sets it on the request context via auth.ContextWithUser
- GetCurrentUser checks context first before falling back to
  session cookie
- Add integration tests for bearer auth user context

internal/service/auth/auth.go

@@ -26,6 +26,21 @@ const (
 	sessionUserID = "user_id"
 )
 
+// contextKeyUser is the context key for storing the authenticated user.
+type contextKeyUser struct{}
+
+// ContextWithUser returns a new context with the given user attached.
+func ContextWithUser(ctx context.Context, user *models.User) context.Context {
+	return context.WithValue(ctx, contextKeyUser{}, user)
+}
+
+// UserFromContext retrieves the user from the context, if set.
+func UserFromContext(ctx context.Context) *models.User {
+	user, _ := ctx.Value(contextKeyUser{}).(*models.User)
+
+	return user
+}
+
 // Argon2 parameters.
 const (
 	argonTime    = 1
@@ -239,6 +254,11 @@ func (svc *Service) GetCurrentUser(
 	ctx context.Context,
 	request *http.Request,
 ) (*models.User, error) {
+	// Check context first (set by bearer token auth).
+	if user := UserFromContext(ctx); user != nil {
+		return user, nil
+	}
+
 	session, sessionErr := svc.store.Get(request, sessionName)
 	if sessionErr != nil {
 		// Session error means no user - this is not an error condition