Prepare Scrollback launch assets and onboarding

[atomtanstudio]

Summary

• Fix SQLite first-run onboarding so README setup can complete with a local SQLite database.
• Scrub legacy FeedSilo runtime fallbacks and align public metadata with Scrollback.
• Add the production launch trailer, poster, feature-card assets, and editable HyperFrames source kit.
• Document the launch asset map, X API account-safety guidance, 9 AM launch plan, and scrollback.atomtan.studio production target.
• Pin patched Hono dependency so the moderate audit finding is resolved.

Verification

• SQLite onboarding smoke test completed end-to-end from a clean temp setup: onboarding page, SQLite connection, migration, admin creation, login session, authenticated home, and expected SQLite tables.
• npm run doctor
• npm run lint
• npm run typecheck
• npm test
• npm run build
• npm audit --audit-level=moderate
• Branding scan found no FeedSilo remnants in tracked project docs/code/assets outside ignored dependency/build output.