fix: Revert lifecycle validation to use hardcoded defaults

## Critical Fix: Terraform Validation Constraint

### Issue
BugBot correctly identified that Terraform validation blocks are isolated
and cannot reference other variables. The previous attempt to use
`var.default_lifecycle_cold_storage_after_days` and
`var.default_lifecycle_delete_after_days` in validation blocks would
cause runtime errors during `terraform plan`/`apply`.

### Root Cause
Terraform variable validation blocks can only reference:
- The variable being validated (e.g., `var.rules`)
- Built-in functions and constants
- NOT other variables from the same configuration

### Solution
Reverted lifecycle validation blocks to use hardcoded defaults:
- `try(rule.lifecycle.cold_storage_after, 0)` (back to hardcoded 0)
- `try(rule.lifecycle.delete_after, 90)` (back to hardcoded 90)

This maintains validation functionality while avoiding the Terraform
limitation. The configurable defaults (`var.default_lifecycle_*`) are
still used correctly in resource creation within `main.tf`.

### Impact
- ✅ Terraform validation now works correctly
- ✅ Resource creation still uses configurable defaults
- ✅ No functional regression in validation logic
- ✅ Prevents runtime errors in terraform plan/apply

### Lesson Learned
Variable validation blocks have strict isolation requirements in Terraform.
Future validation improvements should work within these constraints or
use alternative approaches like locals-based validation in main.tf.

🤖 Generated with [Claude Code](https://claude.ai/code)

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

Author: lgallard

variables.tf

@@ -257,8 +257,8 @@ variable "rules" {
   validation {
     condition = alltrue([
       for rule in var.rules :
-      try(rule.lifecycle.cold_storage_after, var.default_lifecycle_cold_storage_after_days) <= try(rule.lifecycle.delete_after, var.default_lifecycle_delete_after_days) &&
-      try(rule.lifecycle.delete_after, var.default_lifecycle_delete_after_days) >= 1 &&
+      try(rule.lifecycle.cold_storage_after, 0) <= try(rule.lifecycle.delete_after, 90) &&
+      try(rule.lifecycle.delete_after, 90) >= 1 &&
       (try(rule.lifecycle.cold_storage_after, null) == null || rule.lifecycle.cold_storage_after == 0 || rule.lifecycle.cold_storage_after >= 30)
     ])
     error_message = "Lifecycle validation failed: cold_storage_after must be ≤ delete_after, delete_after ≥ 1 day. If cold_storage_after is specified and > 0, it must be ≥ 30 days (AWS requirement). Use 0 to disable cold storage."
@@ -483,8 +483,8 @@ variable "backup_policies" {
   validation {
     condition = alltrue([
       for policy in var.backup_policies :
-      try(policy.lifecycle.cold_storage_after, var.default_lifecycle_cold_storage_after_days) <= try(policy.lifecycle.delete_after, var.default_lifecycle_delete_after_days) &&
-      try(policy.lifecycle.delete_after, var.default_lifecycle_delete_after_days) >= 1 &&
+      try(policy.lifecycle.cold_storage_after, 0) <= try(policy.lifecycle.delete_after, 90) &&
+      try(policy.lifecycle.delete_after, 90) >= 1 &&
       (try(policy.lifecycle.cold_storage_after, null) == null || policy.lifecycle.cold_storage_after == 0 || policy.lifecycle.cold_storage_after >= 30)
     ])
     error_message = "Lifecycle validation failed: cold_storage_after must be ≤ delete_after, delete_after ≥ 1 day. If cold_storage_after is specified and > 0, it must be ≥ 30 days (AWS requirement). Use 0 to disable cold storage."