[dbpatchmanager] Support DBPATCH_HOME env var for binary/install path

[ormico]

Description

Cross-repo prerequisite — action needed in ormico/dbpatchmanager

The dbpatch binary path is currently hardcoded as C:\dbpatch-v2\ in connection configs used by dbexamples. This prevents running dbpatch on Linux or in CI where the binary is installed elsewhere.

Proposed change

Support a DBPATCH_HOME environment variable. Fallback order:

1. DBPATCH_HOME env var if set
2. Current working directory
3. Platform default: C:\dbpatch-v2\ on Windows, /usr/local/bin on Linux

Acceptance criteria

• dbpatch respects DBPATCH_HOME env var
• Existing Windows setups continue to work (backward compatible)
• Works on Linux with DBPATCH_HOME=/usr/local/bin