feat: add local profile setup and settings

[zeapsu]

Summary

• Add a first-run local profile setup flow so new users provide a name and optional context before entering Tome Home.
• Preserve the owner-specific Tome Home greeting by reading the local profile from localStorage, and add a Settings view for editing those details later.
• Extend explicit slash-command routing with /settings and /profile while keeping natural-language prompts in chat.
• Refresh and reorganize project docs under docs/ to reflect current Tome Home, Ethereal Console, BYOA, and explicit-routing direction.
• Reviewed open PRs after Integrate backend generation, live views, and Tome Home #46 landed: closed superseded feat(backend): generation + audio endpoints, session listing, capability prompt #42 and feat(frontend): API client, KB UI, live views, chat routing, history panel #43, left chore: requirements.txt + Agentation dev panel #41 open as requested, and left docs: per-feature reference notes for the sage-app-foundations work #44/feat: add redesigned Tome Home surface #45 open for owner decision.

Test Plan

• cd frontend && npm run test:smoke
• cd frontend && npm run build
• cd backend && uv run --group dev pytest
• git diff --check