feat: Initial MVP with home server identity model

- User model with Ed25519 keypair identity
- Register/login on home server (creates keypair)
- Join guest servers with signature verification
- Public endpoints for cross-server identity
- Channel and message CRUD
- JWT authentication middleware

Architecture: Home server model, no federation, client-driven sync

README.md

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+# Chat Server
+
+A self-hosted Discord alternative with decentralized identity using the Home Server model.
+
+## Architecture
+
+Each user has a **home server** where their identity lives (keypair), and can seamlessly join other **guest servers** using cryptographic signatures.
+
+- **NO identity server** - just use one regular server as "home"
+- **NO federation protocol** - servers don't talk to each other
+- **Client does everything** - syncs, cross-server requests, profile updates
+
+See [ARCHITECTURE.md](./ARCHITECTURE.md) for full details.
+
+## Quick Start
+
+```bash
+# Install dependencies
+dart pub get
+
+# Generate ObjectBox code
+dart run build_runner build
+
+# Run server
+dart run lib/server.dart
+```
+
+## Project Structure
+
+```
+lib/
+├── server.dart              # Entry point, routes
+├── models.dart              # User, Channel, Message entities
+├── objectbox.g.dart         # Generated
+├── config/config.dart       # Server config
+└── src/
+    ├── auth/                # Keypair, JWT, middleware
+    ├── handlers/            # API endpoints
+    └── utils/               # Helpers
+```
+
+## Tech Stack
+
+- **Framework**: Relic 1.0
+- **Database**: ObjectBox
+- **Auth**: JWT + Ed25519 signatures