feat: add PostgreSQL quantum DB integration

[inefabl]

Summary

• Adds the PostgreSQL + Python sidecar Quantum DB implementation under systems/quantum_db/.
• Integrates Qute execution, TN candidate generation, Grover/pyQPanda3 adapters, Wukong preflight/probe workflows, durable jobs, and exact PostgreSQL recheck contracts.
• Adds repository guidance, local configuration templates, PGXS extension sources, smoke scripts, and large-scale benchmark tooling.

Validation

• python3 -m unittest discover -s tests -v — 68 tests passed.
• python3 scripts/qdb_e2e_smoke.py — sidecar routing, candidate extraction, and Qute exact validation passed.
• python3 scripts/qdb_large_scale_benchmark.py --sizes 2000 — benchmark report generated.
• bash -n passed for PostgreSQL and Wukong scripts.

Security and scope

• Removed credential material from tracked configuration; runtime credentials are read only from ORIGINQC_API_KEY.
• Runtime outputs, caches, local databases, native binaries, and training data are ignored.
• Hardware submission remains explicitly authorized and separate from offline tests; PostgreSQL remains the exact result authority.

Please review the new integration boundary and the staged PostgreSQL/Wukong workflows before merging.