docs: add IvorySQL 5 PoWA adaptation guide

[messere1]

Summary

• add bilingual PoWA Archivist 5.3.0 build and deployment guidance for IvorySQL 5
• explain local and recommended remote deployment architectures
• document pg_stat_statements, btree_gist, preload, and track_io_timing setup
• include a reproducible snapshot validation workflow
• document security recommendations and verified Oracle-mode limitations
• add PoWA to both navigation files and ecosystem overview tables

Validation

Validated with IvorySQL 5.4 / PostgreSQL 18.4 and PoWA Archivist 5.3.0:

• source build without PoWA changes — passed
• upstream PostgreSQL regression suite — 8/8 passed
• pg_stat_statements workload capture and powa_take_snapshot — passed
• background worker preload — passed
• Oracle-mode prerequisite installation and identifier-folding limitations — reproduced and documented

Fixes IvorySQL/IvorySQL#1116

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