[codex] improve GitHub project health

[ACCS-0521]

Summary

• add an MIT license and a security reporting policy
• expand the README with architecture, agent workflow, setup, API, project structure, testing, limitations, and roadmap
• add GitHub Actions CI for backend and frontend tests, type checks, and builds
• add structured bug and feature issue forms plus a pull request template
• add weekly Dependabot updates for npm and GitHub Actions
• configure repository topics for discoverability

Why

The repository contained a working MVP but lacked the project-health files and automation expected from a complete public GitHub project. These additions make the project easier to evaluate, run, contribute to, and maintain without changing application behavior.

Validation

• pnpm test — 64 passed, 1 optional live test skipped
• pnpm typecheck
• pnpm build
• pnpm test:web — 4 passed
• pnpm build:web
• parsed all 5 added YAML files successfully
• git diff --check