Refactor API to pure JS and enable offline build/test flow

[caesaralt]

Summary

• replace the TypeScript-based API implementation with plain JavaScript modules that avoid unavailable dependencies while keeping simPRO OAuth endpoints intact
• swap the SQLite job store for a JSON-backed file store and remove external helpers (uuid, string-similarity, pdf-parse) in favour of built-in Node features
• simplify tooling so npm build/test only targets the API workspace and provide node:test based coverage for pricing and idempotency logic

Safety

• simPRO secrets remain server-side; frontend continues to call the backend API only

Verification

• npm run build --workspace=apps/api
• npm run test --workspace=apps/api

Follow-ups

• restore TypeScript linting when registry access is available
• improve PDF parsing fidelity beyond the current text-splitting fallback
• revisit frontend build tooling once dependencies can be installed

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https://chatgpt.com/codex/tasks/task_e_68e62cd9624c832c9d1d450258c7c7da