chore: add Gitea service to docker-compose, fix gitignore

- Gitea (postgres-backed) on ports 3000/2222
- Exclude .claude/ dir and *.db from git
- Update CLAUDE.md with Gitea remote info

docker-compose.prod.yml

@@ -259,8 +259,33 @@ services:
         max-size: "10m"
         max-file: "3"
 
+  gitea:
+    image: gitea/gitea:latest-rootless
+    restart: unless-stopped
+    networks:
+      - scilit
+    volumes:
+      - gitea_data:/var/lib/gitea
+    environment:
+      GITEA__database__DB_TYPE: postgres
+      GITEA__database__HOST: postgres:5432
+      GITEA__database__NAME: gitea
+      GITEA__database__USER: gitea
+      GITEA__database__PASSWD: gitea_pass_2026
+      GITEA__server__DOMAIN: 123.207.9.209
+      GITEA__server__HTTP_PORT: 3000
+      GITEA__server__ROOT_URL: http://123.207.9.209:3000
+      GITEA__server__START_SSH_SERVER: "true"
+      GITEA__server__SSH_DOMAIN: 123.207.9.209
+      GITEA__server__SSH_PORT: 2222
+      GITEA__server__SSH_LISTEN_PORT: 22
+    ports:
+      - "3000:3000"
+      - "2222:22"
+
 volumes:
   pgdata:
   redisdata:
   esdata:
   miniodata:
+  gitea_data: