fix: GITEA_API_TOKEN 从 .env 文件读取，不再硬编码或提交到仓库

- scripts/.env 存储敏感配置（已加入 .gitignore）
- start_dev_agent.sh 启动时自动 source .env
- 环境变量仍可作为 fallback

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

scripts/start_dev_agent.sh

@@ -4,6 +4,12 @@
 
 set -e
 
+# Source local secrets if available (not tracked by git)
+SCRIPT_DIR="$(cd "$(dirname "$0")" && pwd)"
+if [ -f "$SCRIPT_DIR/.env" ]; then
+    source "$SCRIPT_DIR/.env"
+fi
+
 # Load from environment or default values
 export GITEA_API_TOKEN="${GITEA_API_TOKEN:-}"
 export GITEA_URL="${GITEA_URL:-http://localhost:3000}"