feat(matrix): add self-hosted Matrix infrastructure for GDPR compliance

Add complete Matrix/Synapse setup as Telegram bot alternative:

Docker configuration:
- Synapse homeserver (port 8008) with PostgreSQL backend
- Element Web client (port 8087) with ManaCore branding
- DSGVO-compliant data retention policies (1-365 days)
- Prometheus metrics endpoint for monitoring

Config files:
- docker/matrix/homeserver.yaml - Synapse configuration
- docker/matrix/log.config.yaml - Logging with rotation
- docker/matrix/element-config.json - Element Web settings

Scripts & docs:
- scripts/mac-mini/setup-matrix.sh - One-time initialization
- Updated health-check.sh with Matrix services
- Updated MAC_MINI_SERVER.md with Matrix documentation

https://claude.ai/code/session_01E3r5aFW3YLAhEJfsL2ryhv

docker-compose.macmini.yml

@@ -748,6 +748,61 @@ services:
       retries: 3
       start_period: 40s
 
+  # ============================================
+  # Matrix Synapse (Homeserver) - DSGVO-konform
+  # ============================================
+
+  synapse:
+    image: matrixdotorg/synapse:latest
+    container_name: manacore-synapse
+    restart: always
+    depends_on:
+      postgres:
+        condition: service_healthy
+    environment:
+      SYNAPSE_CONFIG_PATH: /data/homeserver.yaml
+      TZ: Europe/Berlin
+      # Secrets (override in .env)
+      SYNAPSE_DB_PASSWORD: ${SYNAPSE_DB_PASSWORD:-synapse-secure-password}
+      SYNAPSE_PASSWORD_PEPPER: ${SYNAPSE_PASSWORD_PEPPER:-change-me-pepper}
+      SYNAPSE_FORM_SECRET: ${SYNAPSE_FORM_SECRET:-change-me-form-secret}
+      SYNAPSE_MACAROON_SECRET: ${SYNAPSE_MACAROON_SECRET:-change-me-macaroon-secret}
+      SYNAPSE_REGISTRATION_SECRET: ${SYNAPSE_REGISTRATION_SECRET:-change-me-registration-secret}
+    volumes:
+      - ./docker/matrix/homeserver.yaml:/data/homeserver.yaml:ro
+      - ./docker/matrix/log.config.yaml:/data/log.config.yaml:ro
+      - synapse_data:/data
+    ports:
+      - "8008:8008"
+      - "9000:9000"
+    healthcheck:
+      test: ["CMD", "curl", "-fSs", "http://localhost:8008/health"]
+      interval: 30s
+      timeout: 10s
+      retries: 3
+      start_period: 60s
+
+  # ============================================
+  # Element Web (Matrix Client)
+  # ============================================
+
+  element-web:
+    image: vectorim/element-web:latest
+    container_name: manacore-element
+    restart: always
+    depends_on:
+      synapse:
+        condition: service_healthy
+    volumes:
+      - ./docker/matrix/element-config.json:/app/config.json:ro
+    ports:
+      - "8087:80"
+    healthcheck:
+      test: ["CMD", "wget", "--no-verbose", "--tries=1", "--spider", "http://localhost:80/"]
+      interval: 30s
+      timeout: 10s
+      retries: 3
+
   # ============================================
   # Auto-Update (Watchtower)
   # ============================================
@@ -786,3 +841,5 @@ volumes:
     name: manacore-grafana
   n8n_data:
     name: manacore-n8n
+  synapse_data:
+    name: manacore-synapse