chore(terraform): align with current terraform standards (charmkeeper)

[seb4stien]

This PR fixes all Terraform modules in synapse-operator (root + 8 sub-modules + product) to align with current standards.

Changes

• Fix Juju provider version to ~> 1.0 across all 11 modules
• Add/fix required_version = "~> 1.12" across all modules
• Enable terraform_required_version tflint rule in all 10 .tflint.hcl files
• Rename model → model_uuid in product module (variables.tf + locals.tf)
• Replace tests/main.tf with tests/setup/main.tf pattern
• Update test to use model_uuid, latest/edge rev 523
• Add missing README.md in modules/postgresql-k8s/ and modules/saml-integrator/
• Add .github/workflows/test_terraform_module.yaml CI workflow (k8s-controller: true)
• Update renovate.json: add ignorePaths: [], remove forbidden terraform-provider rule, fix regex manager

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