feat: add momentry_playground binary for development

- Add separate momentry_playground binary with distinct configuration
- Production (momentry): Port 3002, Redis prefix 'momentry:'
- Development (momentry_playground): Port 3003, Redis prefix 'momentry_dev:'
- Add SERVER_PORT and REDIS_KEY_PREFIX config via environment variables
- Replace all hardcoded Redis key prefixes with configurable values
- Create .env.development for playground environment settings
- Update .env with production defaults
- Add dotenv dependency for environment file loading

Configuration isolation allows running both binaries simultaneously
without port conflicts or Redis key collisions.

.env

@@ -0,0 +1,39 @@
+# Database Configuration
+DATABASE_URL=postgres://accusys@localhost:5432/momentry
+
+# Redis
+# Format: redis://[username][:password]@host:port
+# Users: default (with password), accusys (custom user with password)
+REDIS_URL=redis://accusys:accusys@localhost:6379
+
+# MongoDB
+MONGODB_URL=mongodb://accusys:Test3200Test3200@localhost:27017/admin
+MONGODB_DATABASE=momentry
+
+# Qdrant (not installed, comment out for now)
+# QDRANT_URL=http://localhost:6333
+# QDRANT_COLLECTION=momentry_chunks
+
+# Gitea
+GITEA_URL=http://localhost:3000
+
+# API Server (Production)
+MOMENTRY_SERVER_PORT=3002
+MOMENTRY_REDIS_PREFIX=momentry:
+API_HOST=127.0.0.1
+API_PORT=3002
+
+# Worker Configuration (Production)
+MOMENTRY_WORKER_ENABLED=true
+MOMENTRY_MAX_CONCURRENT=2
+MOMENTRY_POLL_INTERVAL=5
+
+# Watch Directories (comma separated)
+WATCH_DIRECTORIES=~/Videos,~/momentry_core_project/test_video
+
+# Ollama (for Mistral 7B LLM)
+OLLAMA_HOST=http://localhost:11434
+
+# Model Paths
+# EMBEDDING_MODEL_PATH=./models/comic-embed-text
+# LLM_MODEL_PATH=./models/mistral-7b