feat: store Terraform state in Backblaze B2

Configure an s3 backend and initialize Terraform in CI with backend config from Gitea secrets so state persists across runs and apply operations stay consistent.

.gitea/workflows/terraform-apply.yml

@@ -20,6 +20,19 @@ jobs:
           cat > secrets.auto.tfvars << EOF
           pm_api_token_secret = "${{ secrets.PM_API_TOKEN_SECRET }}"
           EOF
+          cat > backend.hcl << EOF
+          bucket                      = "${{ secrets.B2_TF_BUCKET }}"
+          key                         = "terraform.tfstate"
+          region                      = "us-east-005"
+          endpoint                    = "${{ secrets.B2_TF_ENDPOINT }}"
+          access_key                  = "${{ secrets.B2_KEY_ID }}"
+          secret_key                  = "${{ secrets.B2_APPLICATION_KEY }}"
+          skip_credentials_validation = true
+          skip_metadata_api_check     = true
+          skip_region_validation      = true
+          skip_requesting_account_id  = true
+          force_path_style            = true
+          EOF
 
       - name: Set up Terraform
         uses: hashicorp/setup-terraform@v2
@@ -28,7 +41,7 @@ jobs:
 
       - name: Terraform Init
         working-directory: terraform
-        run: terraform init
+        run: terraform init -reconfigure -backend-config=backend.hcl
 
       - name: Terraform Plan
         working-directory: terraform