docs: update README with current architecture, API reference, and deployment guide

[SparkZou]

Summary

Update README.md to reflect the current software architecture and features.

Changes

• Added Architecture section — ASCII diagram showing API Server + Temporal Worker + PostgreSQL topology, component table, and async /memorize flow explanation
• Added full API Reference — Documentation for all 6 endpoints (GET /, POST /memorize, GET /memorize/status/{task_id}, POST /retrieve, POST /clear, POST /categories) with request/response examples
• Added Environment Variables table — All 16 configuration variables with defaults
• Added Makefile Commands — Quick reference for all make targets
• Added Integration Guide — Python and cURL examples showing memorize → poll → retrieve workflow
• Updated Get Started — Restructured into 3 clear steps: start infrastructure, run from source (including worker), run with Docker
• Updated Key Features — Replaced planned/placeholder features with actual implemented capabilities (async Temporal, status tracking, clear, categories)
• Preserved — "Why MemU?" core algorithm section, License, and Community sections unchanged

[Copilot]

Pull request overview

Updates README.md to reflect the current memU-server architecture and provide a fuller end-to-end usage guide aligned with the FastAPI + Temporal + Postgres setup in this repo.

Changes:

• Added an Architecture section explaining the API server/worker split and the async /memorize Temporal flow.
• Expanded “Get Started” with source + Docker instructions, environment variables, and Makefile target quick reference.
• Added an API reference and an integration walkthrough (Python + cURL) for memorize → poll → retrieve.

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[Copilot]

Pull request overview

Copilot reviewed 2 out of 2 changed files in this pull request and generated no new comments.

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