feat: add 'make dev' command to replace dev.sh script

- Auto-installs Air if not found (with GOPATH/bin PATH handling)
- Creates placeholder files for Go embed directive in dev mode
- Starts backend with Air live reload (or falls back to go run)
- Starts frontend with Vite HMR
- Handles cleanup on Ctrl+C/SIGTERM
- Removed dev.sh in favor of unified Makefile command

Author: rishikanthc

Makefile

@@ -1,11 +1,56 @@
-.PHONY: help docs docs-serve docs-clean website website-dev website-build
+.PHONY: help docs docs-serve docs-clean website website-dev website-build dev
 
 help: ## Show this help message
 	@echo 'Usage: make [target]'
 	@echo ''
 	@echo 'Available targets:'
 	@grep -E '^[a-zA-Z_-]+:.*?## .*$$' $(MAKEFILE_LIST) | sort | awk 'BEGIN {FS = ":.*?## "}; {printf "  \033[36m%-20s\033[0m %s\n", $$1, $$2}'
 
+dev: ## Start development environment with Air (backend) and Vite (frontend)
+	@echo "🚀 Starting development environment..."
+	@# Ensure air is installed
+	@if ! command -v air >/dev/null 2>&1; then \
+		echo "⚠️  'air' command not found."; \
+		echo "📦 Auto-installing 'air' for live reload..."; \
+		GOPATH=$$(go env GOPATH); \
+		if [[ ":$$PATH:" != *":$$GOPATH/bin:"* ]]; then \
+			echo "⚠️  $$GOPATH/bin is not in your PATH. Adding it temporarily..."; \
+			export PATH=$$PATH:$$GOPATH/bin; \
+		fi; \
+		go install github.com/air-verse/air@latest; \
+		if ! command -v air >/dev/null 2>&1; then \
+			echo "❌ Failed to install 'air'. Falling back to 'go run'..."; \
+			USE_GO_RUN=true; \
+		else \
+			echo "✅ 'air' installed successfully."; \
+			USE_GO_RUN=false; \
+		fi; \
+	else \
+		USE_GO_RUN=false; \
+	fi; \
+	\
+	mkdir -p internal/web/dist; \
+	if [ -z "$$(ls -A internal/web/dist)" ]; then \
+		echo "📄 Creating placeholder files for Go embed..."; \
+		echo "<!-- Placeholder for development -->" > internal/web/dist/index.html; \
+		echo "placeholder" > internal/web/dist/dummy_asset; \
+	fi; \
+	\
+	trap 'echo ""; echo "🛑 Stopping development servers..."; kill 0; exit 0' INT TERM; \
+	\
+	if [ "$$USE_GO_RUN" = true ]; then \
+		echo "🔧 Starting Go backend (standard run)..."; \
+		go run cmd/server/main.go & \
+	else \
+		echo "🔥 Starting Go backend (with Air live reload)..."; \
+		air & \
+	fi; \
+	\
+	echo "⚛️  Starting React frontend (Vite)..."; \
+	cd web/frontend && npm run dev & \
+	\
+	wait
+
 docs: ## Generate API documentation from Go code annotations
 	@echo "Generating API documentation..."
 	@command -v swag >/dev/null 2>&1 || { echo "Error: swag not installed. Run: go install github.com/swaggo/swag/cmd/swag@latest"; exit 1; }