chore(makefiles): add format-check target and unify formatting logic

- Introduced `format-check` for verification without modification in `llm-gateway` and `knowledge-base` Makefiles.
- Updated `validate` to include `format-check`.
- Added `format-all` to root Makefile for consistent formatting across all components.
- Unexported `VIRTUAL_ENV` to prevent virtual environment warnings.

Makefile

@@ -1,5 +1,5 @@
 .PHONY: help dev dev-full prod down logs logs-dev clean clean-slate drop-db reset-db push-images deploy
-.PHONY: test test-backend test-mcp test-frontend test-all test-cov test-integration validate validate-all
+.PHONY: test test-backend test-mcp test-frontend test-all test-cov test-integration validate validate-all format-all
 
 VERSION ?= latest
 REGISTRY ?= ghcr.io/cardosofelipe/pragma-stack
@@ -22,6 +22,9 @@ help:
 	@echo "  make test-cov      - Run all tests with coverage reports"
 	@echo "  make test-integration - Run MCP integration tests (requires running stack)"
 	@echo ""
+	@echo "Formatting:"
+	@echo "  make format-all    - Format code in backend + MCP servers + frontend"
+	@echo ""
 	@echo "Validation:"
 	@echo "  make validate      - Validate backend + MCP servers (lint, type-check, test)"
 	@echo "  make validate-all  - Validate everything including frontend"
@@ -161,6 +164,25 @@ test-integration:
 	@echo "Note: Requires running stack (make dev first)"
 	@cd backend && RUN_INTEGRATION_TESTS=true IS_TEST=True uv run pytest tests/integration/ -v
 
+# ============================================================================
+# Formatting
+# ============================================================================
+
+format-all:
+	@echo "Formatting backend..."
+	@cd backend && make format
+	@echo ""
+	@echo "Formatting LLM Gateway..."
+	@cd mcp-servers/llm-gateway && make format
+	@echo ""
+	@echo "Formatting Knowledge Base..."
+	@cd mcp-servers/knowledge-base && make format
+	@echo ""
+	@echo "Formatting frontend..."
+	@cd frontend && npm run format
+	@echo ""
+	@echo "All code formatted!"
+
 # ============================================================================
 # Validation (lint + type-check + test)
 # ============================================================================