Add bilingual documentation and streamline README

[Copilot]

Project lacked structured documentation; the README was the sole reference for architecture, configuration, API, and deployment details.

Changes

docs/ folder — 15 new files

Two parallel documentation trees under docs/en/ and docs/it/, each containing:

File	Covers
index.md	Project overview, services table
architecture.md	Service topology, auth flow sequence, token lifecycle, networking
auth-server.md	Full server.js walkthrough — dependencies, OTP logic, middleware, every route with annotated code
nginx.md	Line-by-line default.conf annotation, routing table, security notes
configuration.md	All env vars with defaults, secret-management options, rate-limit tuning
api.md	Endpoint reference with request/response shapes and curl examples
deployment.md	Setup steps, update procedure, troubleshooting, production recommendations

docs/README.md acts as a bilingual entry point linking to both trees.

Root README.md

Reduced from 123 lines to ~30. Retains only a one-paragraph description, a 4-step quick-start block, prerequisites, and a pointer to docs/.

## Documentation
Full documentation (English & Italiano) is available in the [`docs/`](docs/README.md) folder.

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