test: add complex real-world microflow layout examples

New file mdl-examples/doctype-tests/02c-complex-layout-examples.mdl
provides five enterprise-grade microflows for visual layout validation
in Studio Pro, derived from three production Mendix applications:

  CX_VAL_Factory          — multi-field range validation, ~50 activities
  CX_POST_SurveySubmission — guard-chain waterfall, ~40 activities
  CX_ACT_HandleAuthCode   — CASE with nested IF per branch, ~50 activities
  CX_VAL_EmailTemplate    — optional-field format guards, ~35 activities
  CX_ACT_BatchProcessFactories — loop with CASE + nested IF, ~30 activities

CE0111 (duplicate variable name) fixed: retrieve $PostToken then
$PostToken = create ... re-declares the same variable. Changed the
create-branch outputs to $NewPostToken / $NewBasicToken.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: ako