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/app/main.py

@@ -5,9 +5,9 @@ from fastapi import FastAPI
 from fastapi.middleware.cors import CORSMiddleware
 
 from app.core.config import CORS_ORIGINS
-from app.core.discord_bot import start_discord_bot
-from app.core.scheduler import start_scheduler
-from app.core.word_memory import seed_from_history
+from app.core.discord.discord_bot import start_discord_bot
+from app.core.discord.scheduler import start_scheduler
+from app.core.memory_kb.word_memory import seed_from_history
 from app.db.database import SessionLocal, init_db
 from app.db.models import Message
 from app.api import chat, memory, logs, system