📝 Improve README onboarding and self-hosting guidance

[baealex]

🎯 Goal

• Make the README a trustworthy, project-specific entry point for evaluating and running Ocean Brain.
• Align setup, storage, recovery, MCP, and development guidance with current behavior.

🛠️ Core Changes

• Reframe the introduction around Ocean Brain's editor-first connected-note workflow and clarify the live demo's boundaries.
• Add a high-resolution product capture with realistic workspace data, typed properties, inline references, and backlinks.
• Replace the quick start with loopback-safe npx and password-protected Docker examples.
• Document the shared-workspace model, runtime settings, data paths, backups, recovery retention, MCP setup, and development requirements.
• Remove the stale source-production path and present repository commands as a development workflow.

🧠 Key Decisions

• Keep the README focused on user workflows and operational boundaries instead of exhaustive feature or MCP tool inventories.
• Use safe copy-paste defaults and clearly separate packaged self-hosting from source development.
• Use the existing Ocean Brain icon, an authentic product screen, and concise project-specific language instead of badges or generic product claims.

🧪 Verification Guide

How to verify

1. Render README.md and review its icon, product screenshot, internal navigation, tables, Bash examples, and MCP JSON example.
2. Run pnpm check:encoding, pnpm lint, and pnpm test:ci.
3. Run pnpm type-check, pnpm build, and git diff --check.

Expected result

• The README presents safe local defaults, accurate storage and recovery details, and the current MCP setup flow.
• The product screenshot stays legible at README width and shows the editor-first workflow without browser or development chrome.
• Encoding, lint, all tests, type-check, build, and diff checks pass.
• README Bash and JSON syntax checks pass, and all local and external links resolve.

✅ Checklist

• Lint completed
• Type-check completed
• Tests completed
• Documentation updated