feat(catalog): add Kan.bn app

[SulimanAbdulrazzaq]

Summary

Adds Kan.bn as an available one-click app in the Openship catalog.

Motivation

Issue #513 requests a self-hosted Kan.bn deployment. The template follows Kan.bn's official repository and Docker Compose configuration: PostgreSQL 15, the migration image, and the web image with generated secrets and the documented public endpoint.

Related issue

Closes #513

Changes

• Added packages/core/src/apps/catalog/kanbn.json with the official Kan.bn services, dependencies, Postgres healthcheck, persistent volume, generated POSTGRES_PASSWORD and BETTER_AUTH_SECRET, and web endpoint.
• Regenerated packages/core/src/apps/catalog.json.
• Added a catalog contract test covering the Kan.bn service wiring and generated secrets.

Verification

packages/core full test suite (Vitest, --testTimeout 120000): 35 files, 420 tests passed
apps/api/test/lib/app-templates.test.ts: 6 tests passed
apps/api TypeScript: tsc --noEmit -p apps/api/tsconfig.json passed
packages/core TypeScript: tsc --noEmit -p packages/core/tsconfig.json passed
git diff --check passed

Checklist

• One change per PR — one agreed feature, with nothing unrelated bundled in
• The diff is scoped — no reformatting or lint fixes on lines I wasn't otherwise changing
• A test fails without this change and passes with it
• Relevant tests, typechecks, and formatting checks pass locally
• I understand every line of this diff and can explain it in review