Intent router — consolidate routing and add Ollama local reasoning

[chansg]

Currently brain.py contains a partial LOCAL_INTENTS dict with weather keyword checking. No separate router.py exists yet. Required:

1. Build core/router.py as the single source of truth for intent classification
2. Move all intent matching out of brain.py into router.py
3. Wire Ollama local model (mistral) as the primary reasoning engine for web queries
4. Claude API called only for complex reasoning and personality development
5. DuckDuckGo scraping via Playwright as the web retrieval layer

Tier system: datetime → free, web lookup → scrape + Ollama, complex → Claude.

Acceptance criteria: Claude API not called for weather, time, date, calendar, or simple web lookups.