fix: implement mode=get_scripts

[thedancingdeveloper]

Summary

Fixes #74: mode=get_scripts is a real, top-level SABnzbd API mode (sabnzbd/api.py:1107, _api_table["get_scripts"] = (_api_get_scripts, 2)) that RustNZB didn't handle — it fell through dispatch_mode's default arm and returned {"status": false, "error": "Unknown mode: get_scripts"}.

# sabnzbd/api.py:796-797
def _api_get_scripts(name, kwargs):
    return report(keyword="scripts", data=list_scripts())

With no script directory / no scripts present, real SABnzbd's list_scripts() returns ["None"] — RustNZB doesn't support post-processing scripts at all, so that's the correct permanent response here too.

Impact

Several SAB-compatible clients (including download-from-search "add" dialogs) fetch categories and scripts together to populate the add dialog, and some abort populating the whole dialog — category picker included — if either call errors. Possibly a second contributor to #65, alongside #73.

Fix

dispatch_mode now answers get_scripts with {"scripts": ["None"]}.

Test plan

• cargo test -p nzb-web — added get_scripts_reports_none_when_unsupported.
• cargo clippy -p nzb-web --all-targets — clean.
• Full nzb-web test suite passes.

🤖 Generated with Claude Code

[thedancingdeveloper]

Superseded — this change landed via #84, which stacked all of #71-#77's fixes together and was squash-merged to save on redundant CI runs. Closing without merging to avoid re-applying the same diff.