feat(jobs): persist async batch job state in PostgreSQL

- Add jobs table to database schema (job_id, status, progress, result_json, etc.)
- Add DatabaseClient methods: create_job, update_job, get_job, list_jobs
- Add mark_stale_jobs_failed() called at startup to handle interrupted jobs
- Refactor _run_batch_job and job endpoints to read/write from PostgreSQL
- Remove in-memory _jobs dict; job state now survives API restarts
- Update init_database.py to list all tables in output

Closes leeworks-agents/SPARC#8

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

scripts/init_database.py

@@ -40,6 +40,9 @@ def main():
         print("\nTables created:")
         print("  - llm_messages: Stores all LLM prompts and responses")
         print("  - users: Stores user accounts")
+        print("  - jobs: Stores async batch job state")
+        print("  - patents: Patent PDF cache")
+        print("  - serp_queries: SERP query result cache")
         print("\nIndexes created:")
         print("  - idx_messages_timestamp: For time-based queries")
         print("  - idx_messages_company: For company-specific queries")