fix(migration): properly transform v3 flat structure to v4 nested snmp config

The v3→v4 migration was only renaming upsList to upsDevices without
transforming the device structure. V3 had a flat structure with SNMP
fields directly on the device object, while v4 expects a nested 'snmp'
object.

This commit fixes the migration to:
- Move host, port, community, version, etc. into nested snmp object
- Convert version from string to number
- Add default timeout (5000ms)
- Create thresholds object with defaults
- Preserve all SNMPv1, v2c, and v3 authentication fields

Also includes install.sh fix for better non-interactive handling.

deno.json

@@ -1,6 +1,6 @@
 {
   "name": "@serve.zone/nupst",
-  "version": "4.0.3",
+  "version": "4.0.4",
   "exports": "./mod.ts",
   "tasks": {
     "dev": "deno run --allow-all mod.ts",