Remove Docker support - focus on Nix-based development

This library uses Nix for development environment management.
Docker-based setup added unnecessary complexity for a library package.

Removed:
- Dockerfile (library packages don't need containerization)
- .dockerignore (no longer needed)
- .github/docker/Dockerfile.postgres (Nix provides PostgreSQL+pgmq)
- .github/workflows/docker-build.yml (no Docker images to build)

Updated:
- Makefile: Remove all Docker commands, fix project name
- SETUP.md: Remove Docker installation method, emphasize Nix
- QUICKREF.md: Remove Docker commands section
- docs/DEPLOYMENT_GUIDE.md: Simplify Docker reference
- scripts/README.md: Fix project name reference

Summary:
- Removed 368 lines of Docker-related code
- Simplified documentation to focus on Nix workflow
- Library packages should be added as dependencies, not containerized
- Users containerize their own applications, not the library itself

Development now uses:
- Primary: Nix (recommended - includes everything)
- Fallback: Native installation for advanced users

Author: claude

.dockerignore

@@ -1,14 +1,13 @@
-.PHONY: help setup test quality clean docker-up docker-down
+.PHONY: help setup test quality clean
 
 # Default target
 help:
-	@echo "ExPgflow Development Commands"
-	@echo "=============================="
+	@echo "Singularity.Workflow Development Commands"
+	@echo "=========================================="
 	@echo ""
 	@echo "Setup:"
 	@echo "  make setup          - Set up development environment (interactive)"
 	@echo "  make setup-nix      - Set up using Nix"
-	@echo "  make setup-docker   - Set up using Docker (PostgreSQL only)"
 	@echo ""
 	@echo "Development:"
 	@echo "  make deps           - Install dependencies"
@@ -23,12 +22,6 @@ help:
 	@echo "  make db-reset       - Reset database"
 	@echo "  make db-shell       - Open PostgreSQL shell"
 	@echo ""
-	@echo "Docker:"
-	@echo "  make docker-up      - Start PostgreSQL with Docker"
-	@echo "  make docker-down    - Stop PostgreSQL"
-	@echo "  make docker-logs    - View PostgreSQL logs"
-	@echo "  make docker-reset   - Reset Docker environment"
-	@echo ""
 	@echo "Formatting & Linting:"
 	@echo "  make format         - Format code"
 	@echo "  make lint           - Run Credo linter"
@@ -51,9 +44,6 @@ setup:
 setup-nix:
 	@./scripts/setup-dev-environment.sh --method nix
 
-setup-docker:
-	@./scripts/setup-dev-environment.sh --method docker
-
 # Dependencies
 deps:
 	@echo "Installing dependencies..."
@@ -122,29 +112,6 @@ db-shell:
 	@echo "Opening PostgreSQL shell..."
 	@psql $(DATABASE_URL)
 
-# Docker
-docker-up:
-	@echo "Starting PostgreSQL with Docker..."
-	@docker-compose up -d
-	@echo "Waiting for PostgreSQL to be ready..."
-	@sleep 3
-	@docker-compose exec -T postgres pg_isready -U postgres || (echo "PostgreSQL not ready" && exit 1)
-	@echo "✓ PostgreSQL is ready"
-	@echo "Database URL: postgresql://postgres:postgres@localhost:5433/postgres"
-
-docker-down:
-	@echo "Stopping PostgreSQL..."
-	@docker-compose down
-	@echo "✓ PostgreSQL stopped"
-
-docker-logs:
-	@docker-compose logs -f
-
-docker-reset:
-	@echo "Resetting Docker environment..."
-	@docker-compose down -v
-	@echo "✓ Docker environment reset"
-
 # Documentation
 docs:
 	@echo "Generating documentation..."

.github/docker/Dockerfile.postgres

@@ -73,22 +73,6 @@ make db-reset
 make db-shell
 ```
 
-## Docker Commands
-
-```bash
-# Start PostgreSQL
-make docker-up
-
-# Stop PostgreSQL
-make docker-down
-
-# View logs
-make docker-logs
-
-# Reset (delete all data)
-make docker-reset
-```
-
 ## Common Tasks
 
 ### Running Tests
@@ -159,9 +143,6 @@ make check
 # Check PostgreSQL is running
 pg_isready -h localhost
 
-# Start PostgreSQL (Docker)
-make docker-up
-
 # Reset database
 make db-reset
 ```
@@ -271,10 +252,7 @@ make check
 ### "pgmq extension not found"
 
 ```bash
-# Use Docker with pgmq
-make docker-up
-
-# Or use Nix
+# Use Nix (includes PostgreSQL with pgmq)
 nix develop
 ```
 
@@ -291,10 +269,10 @@ nix develop
 ### "Connection refused" (PostgreSQL)
 
 ```bash
-# Start PostgreSQL
-make docker-up
+# Use Nix (auto-starts PostgreSQL)
+nix develop
 
-# Or check system PostgreSQL
+# Or start system PostgreSQL
 sudo systemctl start postgresql  # Linux
 brew services start postgresql   # macOS
 ```