Support saving httpx results to PostgreSQL

[coderabbitai]

Description

Support saving httpx results to PostgreSQL database, similar to nuclei's database reporting feature.

This is a sub-task of #1973.

Implementation

Add PostgreSQL database support for persisting httpx scan results with a flag like:

-rdb, -report-db string       httpx reporting database (always use this to persist report data)

Parent Issue

• Support saving httpx results to database #1973 - Support saving httpx results to database
• Support saving httpx results to database #1973

cc @ipsecc