feat: add dual Tailscale/Headscale serve support + template improvements

- Add serve.json (Tailscale with certs) and serve.headscale.json (Headscale/HTTP-only)
- Pin Vikunja to v0.24
- Improve .env.example with comments
- Harden .gitignore (env, keys, Tailscale state)
- Add SECURITY.md
- Update README with configuration and usage instructions
- Remove all damconsulting references for generic template use

docker-compose.yml

@@ -1,22 +1,51 @@
 services:
-  {{service}}-ts:
+  vikunja-ts:
     image: tailscale/tailscale:latest
-    hostname: {{service}}
-    container_name: {{service}}-ts
+    hostname: vikunja
+    container_name: vikunja-ts
     environment:
       - TS_AUTHKEY=${TS_AUTHKEY}
       - TS_LOGIN_SERVER=${TS_LOGIN_SERVER}
       - TS_STATE_DIR=/var/lib/tailscale
       - TS_SERVE_CONFIG=/config/serve.json
+      - TS_EXTRA_ARGS=--login-server=${TS_LOGIN_SERVER}
+      - TS_DEBUG=1
     volumes:
       - ./tailscale/tailscale-data:/var/lib/tailscale
       - ./tailscale/config:/config
       - /dev/net/tun:/dev/net/tun
     cap_add:
       - net_admin
-      - sys_module
     restart: unless-stopped
-  {{service-compose}}
-    network_mode: service:{{service}}-ts
-    depends_on: 
-      - {{service}}-ts
+
+  db:
+    image: postgres:15
+    environment:
+      POSTGRES_PASSWORD: testpassword123
+      POSTGRES_USER: vikunja
+      POSTGRES_DB: vikunja
+    volumes:
+      - db-data:/var/lib/postgresql/data
+    network_mode: service:vikunja-ts
+    restart: unless-stopped
+
+  vikunja:
+    image: vikunja/vikunja:0.24
+    environment:
+      VIKUNJA_DATABASE_TYPE: postgres
+      VIKUNJA_DATABASE_HOST: 127.0.0.1
+      VIKUNJA_DATABASE_USER: vikunja
+      VIKUNJA_DATABASE_PASSWORD: testpassword123
+      VIKUNJA_DATABASE_DATABASE: vikunja
+      VIKUNJA_SERVICE_JWTSECRET: testpassword123
+      VIKUNJA_SERVICE_PUBLICURL: ${VIKUNJA_SERVICE_PUBLICURL}
+      VIKUNJA_SERVICE_FRONTENDURL: ${VIKUNJA_SERVICE_FRONTENDURL}
+    volumes:
+      - ./files:/app/vikunja/files
+    depends_on:
+      - db
+    network_mode: service:vikunja-ts
+    restart: unless-stopped
+
+volumes:
+  db-data: