Reorganize core into subpackages, add local KB, ruff/pyright tooling

- Split backend/app/core into weather/, discord/, memory_kb/, search/
  subpackages by responsibility, keeping config.py and llm.py as the
  shared foundation; updated all import sites accordingly.
- Add local Markdown knowledge base support (local_knowledge.py,
  knowledge_base/fgo.md, LOCAL_KB_* settings) that embeds and injects
  relevant docs into the system prompt by topic similarity.
- Add ruff and pyright as backend dev dependencies with basic config
  in pyproject.toml for linting and type checking.
- Document local machine quirks in CLAUDE.md (Postgres on port 8080,
  SSLKEYLOGFILE breaking litellm/pyright via OPENSSL_Uplink crashes).
- Add backend/run_dev.ps1 dev launcher and docs/discord-bot.md.

backend/.env.example

@@ -21,6 +21,13 @@ TAVILY_API_KEY=
 # 蓄積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=15
 
+# ローカルMarkdownナレッジベース（backend/knowledge_base/ 配下のファイルを話題に応じて注入）
+LOCAL_KB_DIR=knowledge_base
+# Ollamaを使う場合は ollama/nomic-embed-text のように指定（OLLAMA_API_BASEも参照される）
+LOCAL_KB_EMBEDDING_MODEL=text-embedding-3-small
+LOCAL_KB_TOP_K=3
+LOCAL_KB_MIN_SCORE=0.75
+
 # 天気予報 → Discord 通知
 DISCORD_WEBHOOK_URL=
 WEATHER_AREA_CODE=120000