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.

.claude/settings.local.json

@@ -5,7 +5,13 @@
       "Bash(ls \"C:\\\\Users\\\\Yuya Suzuki\\\\AppData\\\\Roaming\\\\Claude\\\\\")",
       "WebSearch",
       "Bash(uv add *)",
-      "Bash(git check-ignore *)"
+      "Bash(git check-ignore *)",
+      "Bash(uv run python -c ' *)",
+      "Bash(PYTHONIOENCODING=utf-8 uv run python -c ' *)",
+      "Bash(curl -s http://localhost:8010/docs -o /dev/null -w \"status:%{http_code}\\\\n\")",
+      "Bash(git add *)",
+      "Bash(git commit -m ' *)",
+      "PowerShell(Get-Process | Where-Object { $_.ProcessName -match \"python|uvicorn\" } | Select-Object Id, ProcessName, Path)"
     ]
   }
 }