Add Docker/Lightsail deployment, web search summarization, and fix vite peer dep

- Add backend/frontend Dockerfiles, nginx reverse proxy config, and
  docker-compose.yml to run the app on AWS Lightsail; document the setup
  in docs/deploy-lightsail.md. Fix a .gitignore path anchoring bug that
  left backend/knowledge_base/web_search/ untracked instead of ignored.
- Summarize web search results into structured Markdown via LLM before
  saving them to the local knowledge base, and support regenerating
  existing entries from their source URLs (backend/app/core/memory_kb).
- Downgrade vite to ^6 to match @vitejs/plugin-vue's peer dependency
  range, fixing a failing `npm ci` (found while testing the Docker build).

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

backend/app/core/config.py

@@ -16,6 +16,8 @@ TAGGING_MODEL: str | None = os.getenv("TAGGING_MODEL")
 TAVILY_API_KEY: str | None = os.getenv("TAVILY_API_KEY")
 # 蓄積した知識をシステムプロンプトに注入する際の最大件数
 KNOWLEDGE_CONTEXT_LIMIT: int = int(os.getenv("KNOWLEDGE_CONTEXT_LIMIT", "15"))
+# Web検索結果を構造的な要約にまとめる際に使うモデル（未設定ならDEFAULT_MODELを使用）
+SEARCH_SUMMARY_MODEL: str | None = os.getenv("SEARCH_SUMMARY_MODEL")
 
 # ローカルMarkdownナレッジベース（話題に応じて関連ファイルをシステムプロンプトに注入）
 LOCAL_KB_DIR: str = os.getenv("LOCAL_KB_DIR", "knowledge_base")