docs: update readme

README.md

@@ -11,6 +11,14 @@ A secure, self-hostable "burn after reading" paste service with ephemeral storag
 - Fast and reliable
 - Written in Gleam (type-safe)
 
+## Architecture
+
+- Gleam: Type-safe language built upon the BEAM
+- Web: Wisp framework + Mist HTTP server
+- Frontend: Lustre for HTML rendering
+- Storage: In-memory only (no persistence)
+- Security: AES-256-GCM client-side encryption, CSRF tokens, rate limiting, security headers
+
 ## Configuration
 
 ### SECRET_KEY_BASE (Required for Production)
@@ -50,6 +58,29 @@ gleam run
 
 The server starts on `http://localhost:3000`.
 
+## Docker image+deployment
+
+### Build
+
+```bash
+docker build -t spasteg .
+```
+
+### Run
+
+```bash
+# Generate a secure key
+docker run -p 3000:3000 -e SECRET_KEY_BASE=$(openssl rand -base64 48) spasteg
+```
+
+**With custom port:**
+
+```bash
+docker run -p 8080:3000 -e SECRET_KEY_BASE=$(openssl rand -base64 48) -e PORT=3000 spasteg
+```
+
+The container exposes port 3000 and runs as a non-root user with a health check configured.
+
 ## Usage
 
 1. Visit `http://localhost:3000`
@@ -60,27 +91,6 @@ The server starts on `http://localhost:3000`.
 
 Note: the creator cannot see their post with the copied link (except in private browsing) - it would be burned immediately.
 
-## Architecture
-
-- **Gleam**: Type-safe language built upon the BEAM
-- **Web**: Wisp framework + Mist HTTP server
-- **Frontend**: Lustre for HTML rendering
-- **Storage**: In-memory only (no persistence)
-- **Security**: AES-256-GCM client-side encryption, CSRF tokens, rate limiting, security headers
-
-## Security Notes
-
-- Pastes are client-side encrypted (AES-256-GCM) before being sent to server
-- Server never sees the decryption key (stored in URL fragment after `#`)
-- Data is stored **encrypted** in server memory only
-- Data is **never written to disk**
-- All data is lost on server restart
-- CSRF protection via double-submit cookie pattern
-- Rate limiting: 10 requests per IP (resets on server restart)
-- Security headers: CSP, X-Frame-Options, X-Content-Type-Options, Referrer-Policy
-- 10MB maximum paste size limit
-- Intended for ephemeral sharing only — do not store sensitive data
-
 ## License
 
 This project is licensed under the GNU General Public License v3.0 or later (GPLv3+). See the [LICENSE](LICENSE) file for details.