Publish source and community builder gateway

[rback37]

What changed

• Publishes the runnable Debt World application source, database schema and migrations, worker entrypoint, tests, and public launch assets.
• Adds the GNU AGPL-3.0-or-later license plus bilingual contribution, governance, conduct, security, and support boundaries.
• Adds the bilingual /contribute and /en/contribute gateways so people can help through translation, regional debt-category review, device testing, accessibility, privacy review, or code.
• Adds Issue and Discussion templates and connects the repository README to the public builder flow.

Why

Debt World is meant to grow through real, privacy-safe contributions from different countries—not only through one founder. Publishing a reviewed runnable source tree makes the invitation concrete and lets contributors inspect the product before volunteering.

User and developer impact

• Contributors can run the project locally with Node.js 22.13+.
• Non-code contributors have clear 10–30 minute first tasks.
• Production secrets, exact financial records, private AI conversations, recovery codes, administrator access, and user data remain outside the repository.
• Network deployments of modified versions remain covered by AGPL source-sharing obligations.

Validation

• npm ci --prefer-offline
• npm run lint
• npm run build
• npm test — 7/7 server tests passed
• Tracked-source secret-prefix scan completed; no real API key or environment file was included.

This is intentionally a draft PR so the initial public-source publication can be reviewed before merge.