docs: add complete guide, env files, fix docker-compose

- Add GUIDE.md: complete user documentation covering installation,
  Docker deployment, AI providers, MCP server, N8N integration,
  email config, admin panel, env var reference, troubleshooting
- Add mcp-server/.env.example with all MCP-specific variables
- Update .env.docker.example with all 42 environment variables
- Fix docker-compose.yml: parameterize PostgreSQL credentials,
  add missing env vars (CUSTOM_OPENAI, AI_PROVIDER_CHAT,
  ALLOW_REGISTRATION, RESEND_API_KEY)
- Track memento-note/.env.example

docker-compose.yml

@@ -7,15 +7,15 @@ services:
     container_name: memento-postgres
     restart: unless-stopped
     environment:
-      POSTGRES_USER: keepnotes
-      POSTGRES_PASSWORD: keepnotes
-      POSTGRES_DB: keepnotes
+      POSTGRES_USER: ${POSTGRES_USER:-memento}
+      POSTGRES_PASSWORD: ${POSTGRES_PASSWORD:-memento}
+      POSTGRES_DB: ${POSTGRES_DB:-memento}
     volumes:
       - postgres-data:/var/lib/postgresql/data
     ports:
       - "5432:5432"
     healthcheck:
-      test: ["CMD-SHELL", "pg_isready -U keepnotes"]
+      test: ["CMD-SHELL", "pg_isready -U ${POSTGRES_USER:-memento}"]
       interval: 5s
       timeout: 5s
       retries: 5
@@ -35,7 +35,7 @@ services:
     ports:
       - "3000:3000"
     environment:
-      - DATABASE_URL=postgresql://keepnotes:keepnotes@postgres:5432/keepnotes
+      - DATABASE_URL=postgresql://${POSTGRES_USER:-memento}:${POSTGRES_PASSWORD:-memento}@postgres:5432/${POSTGRES_DB:-memento}
       - NEXTAUTH_SECRET=${NEXTAUTH_SECRET:-changethisinproduction}
       - NEXTAUTH_URL=${NEXTAUTH_URL:-http://localhost:3000}
       - NODE_ENV=production
@@ -51,11 +51,16 @@ services:
       # AI Providers
       - AI_PROVIDER_TAGS=${AI_PROVIDER_TAGS}
       - AI_PROVIDER_EMBEDDING=${AI_PROVIDER_EMBEDDING}
+      - AI_PROVIDER_CHAT=${AI_PROVIDER_CHAT}
       - OPENAI_API_KEY=${OPENAI_API_KEY}
       - OLLAMA_BASE_URL=${OLLAMA_BASE_URL}
-      - OLLAMA_MODEL=${OLLAMA_MODEL}
       - AI_MODEL_TAGS=${AI_MODEL_TAGS}
       - AI_MODEL_EMBEDDING=${AI_MODEL_EMBEDDING}
+      - AI_MODEL_CHAT=${AI_MODEL_CHAT}
+      - CUSTOM_OPENAI_API_KEY=${CUSTOM_OPENAI_API_KEY}
+      - CUSTOM_OPENAI_BASE_URL=${CUSTOM_OPENAI_BASE_URL}
+      - ALLOW_REGISTRATION=${ALLOW_REGISTRATION:-true}
+      - RESEND_API_KEY=${RESEND_API_KEY}
     volumes:
       - uploads-data:/app/public/uploads
     depends_on:
@@ -97,7 +102,7 @@ services:
       - MCP_MODE=${MCP_MODE:-stdio}
       - PORT=${MCP_PORT:-3001}
       # Database - connect to shared PostgreSQL
-      - DATABASE_URL=postgresql://keepnotes:keepnotes@postgres:5432/keepnotes
+      - DATABASE_URL=postgresql://${POSTGRES_USER:-memento}:${POSTGRES_PASSWORD:-memento}@postgres:5432/${POSTGRES_DB:-memento}
       - NODE_ENV=production
     depends_on:
       postgres: