Add .deb packaging, GitHub Actions CI/CD, and release workflows

- Makefile: add 'deb' and 'release' targets; fix migrate/create syntax
- scripts/build-deb.sh: build .deb with systemd unit, postinst/prerm/postrm
- .github/workflows/ci.yml: go build, test, lint on PR/push to main
- .github/workflows/release.yml: multi-platform build (linux/darwin/windows
  × amd64/arm64), .deb for Linux, tarballs, draft GitHub Release on tag v*
- README.md: add CI/Release badges, Install section with .deb and binary
  release instructions

Makefile

@@ -1,4 +1,4 @@
-.PHONY: build run test lint clean migrate dev prod deps fmt
+.PHONY: build run test lint clean migrate dev prod deps fmt deb release
 
 # Binary name
 BINARY=llamalink
@@ -8,7 +8,9 @@ LDFLAGS=-ldflags "-X main.Version=$(VERSION) -X main.BuildTime=$(BUILD_TIME)"
 
 # Directories
 BUILD_DIR=./bin
+DIST_DIR=./dist
 FRONTEND_DIR=./web/frontend
+DEB_ARCH=$(shell dpkg --print-architecture 2>/dev/null || echo "amd64")
 
 # Go parameters
 GOCMD=go
@@ -60,7 +62,7 @@ deps:
 
 ## clean: Remove build artifacts
 clean:
-	rm -rf $(BUILD_DIR)
+	rm -rf $(BUILD_DIR) $(DIST_DIR)
 	rm -f coverage.out
 	rm -f *.db
 
@@ -72,8 +74,9 @@ migrate/up:
 migrate/down:
 	migrate -path internal/db/migrations -database "$(DATABASE_URL)" down
 
-## migrate/create: Create a new migration
-migrate/create NAME=add_users_table:
+## migrate/create: Create a new migration (Usage: make migrate/create NAME=add_users_table)
+migrate/create:
+	@if [ -z "$(NAME)" ]; then echo "Usage: make migrate/create NAME=add_users_table"; exit 1; fi
 	migrate create -path internal/db/migrations -ext .sql -dir internal/db/migrations $(NAME)
 
 ## frontend/install: Install frontend dependencies
@@ -99,6 +102,19 @@ docker/run:
 ## docker/build/run: Build and run with docker-compose
 docker/build/run: docker/build docker/run
 
+## deb: Build .deb package (requires dpkg-deb, Linux only)
+deb: build
+	@echo "Building .deb package..."
+	@./scripts/build-deb.sh $(VERSION) $(DEB_ARCH)
+
+## release: Build all release artifacts locally
+release:
+	@echo "Building release artifacts for $(VERSION)..."
+	@mkdir -p $(DIST_DIR)
+	$(MAKE) build
+	$(MAKE) deb
+	@echo "Release artifacts in $(DIST_DIR)/"
+
 ## help: Show this help
 help:
 	@grep -E '^[a-zA-Z_-]+:.*?## .*$$' $(MAKEFILE_LIST) | sort | awk 'BEGIN {FS = ":.*?## "}; {printf "\033[36m%-20s\033[0m %s\n", $$1, $$2}'