fix: resolve Docker build failure and clarify env var configuration

- Remove .env file with incorrect CLAUDE_CODE_MAX_TOKENS variable
- Remove .env copy from Dockerfile that was causing build to fail
- Update README to distinguish local (export) vs Docker (-e) env var usage
- Add CLAUDE_CODE_MAX_OUTPUT_TOKENS to all Docker run examples

The correct variable is CLAUDE_CODE_MAX_OUTPUT_TOKENS (not CLAUDE_CODE_MAX_TOKENS)
and should be passed at runtime via -e flag for Docker or export for local runs.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

Dockerfile

@@ -109,7 +109,6 @@ WORKDIR /app
 
 # Copy package.json and package-lock.json first for better caching
 COPY package*.json ./
-COPY .env ./.env
 
 # Install Node.js dependencies as root
 RUN npm ci --only=production && \