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-plan.yml

@@ -22,6 +22,19 @@ 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
           echo "Created secrets.auto.tfvars:"
           cat secrets.auto.tfvars | sed 's/=.*/=***/'
           echo "Using token ID from terraform.tfvars:"
@@ -34,7 +47,7 @@ jobs:
 
       - name: Terraform Init
         working-directory: terraform
-        run: terraform init
+        run: terraform init -reconfigure -backend-config=backend.hcl
 
       - name: Terraform Format Check
         working-directory: terraform