ci(infrastructure): add TFLint configuration with azurerm plugin (#209)

## Description

Added a `.tflint.hcl` configuration file at the repository root,
establishing Terraform linting for `deploy/001-iac/` and its child
modules. Configured TFLint v0.61.0+ with the **azurerm** plugin v0.31.1
and the **terraform recommended** preset. Disabled
`terraform_comment_syntax` to preserve the repository's existing `//`
and `/* */` comment conventions, and enabled documentation and naming
convention enforcement rules.

Closes #200

## Type of Change

- [ ] 🐛 Bug fix (non-breaking change fixing an issue)
- [x] ✨ New feature (non-breaking change adding functionality)
- [ ] 💥 Breaking change (fix or feature causing existing functionality
to change)
- [ ] 📚 Documentation update
- [x] 🏗️ Infrastructure change (Terraform/IaC)
- [ ] ♻️ Refactoring (no functional changes)

## Component(s) Affected

- [ ] `deploy/000-prerequisites` - Azure subscription setup
- [x] `deploy/001-iac` - Terraform infrastructure
- [ ] `deploy/002-setup` - OSMO control plane / Helm
- [ ] `deploy/004-workflow` - Training workflows
- [ ] `src/training` - Python training scripts
- [ ] `docs/` - Documentation

## Testing Performed

- [ ] Terraform `plan` reviewed (no unexpected changes)
- [ ] Terraform `apply` tested in dev environment
- [ ] Training scripts tested locally with Isaac Sim
- [ ] OSMO workflow submitted successfully
- [ ] Smoke tests passed (`smoke_test_azure.py`)

> `tflint --init` verified — azurerm plugin downloaded successfully.

## Documentation Impact

- [x] No documentation changes needed
- [ ] Documentation updated in this PR
- [ ] Documentation issue filed

## Bug Fix Checklist

*Complete this section for bug fix PRs. Skip for other contribution
types.*

- [ ] Linked to issue being fixed
- [ ] Regression test included, OR
- [ ] Justification for no regression test:

## Checklist

- [x] My code follows the [project conventions](copilot-instructions.md)
- [x] Commit messages follow [conventional commit
format](instructions/commit-message.instructions.md)
- [x] I have performed a self-review
- [x] Documentation impact assessed above
- [x] No new linting warnings introduced

---------

Co-authored-by: Bill Berry <WilliamBerryiii@users.noreply.github.com>

Author: katriendg

.gitignore

@@ -410,6 +410,9 @@ FodyWeavers.xsd
 # Ignore .terraform lock
 .terraform.lock.hcl
 
+# TFLint plugin cache
+.tflint.d/
+
 # Crash log files
 crash.log
 

.tflint.hcl

@@ -0,0 +1,45 @@
+/** TFLint configuration for deploy/001-iac and child modules */
+
+tflint {
+  required_version = ">= 0.61.0"
+}
+
+config {
+  /* call local modules so modules/ subdirectories are also linted */
+  call_module_type = "local"
+  format           = "compact"
+}
+
+/* bundled terraform ruleset — recommended preset excludes terraform_comment_syntax */
+plugin "terraform" {
+  enabled = true
+  preset  = "recommended"
+}
+
+/* azurerm ruleset — only available plugin for this provider stack */
+plugin "azurerm" {
+  enabled = true
+  version = "0.31.1"
+  source  = "github.com/terraform-linters/tflint-ruleset-azurerm"
+}
+
+// terraform_comment_syntax: repo uses // and /* */ comments, not #
+rule "terraform_comment_syntax" {
+  enabled = false
+}
+
+// terraform_documented_variables: require description on all variable blocks
+rule "terraform_documented_variables" {
+  enabled = true
+}
+
+// terraform_documented_outputs: require description on all output blocks
+rule "terraform_documented_outputs" {
+  enabled = true
+}
+
+/* terraform_naming_convention: enforce snake_case across all block types */
+/* note: cannot scope to bool-typed variables only — snake_case is TFLint maximum */
+rule "terraform_naming_convention" {
+  enabled = true
+}