Persist config files across Opus package updates

The Opus package manager deletes the entire package directory on
update (fs.delete(packageDir)) before re-downloading files. This
wiped all config files (.manager_config, .client_config, etc.) that
were stored inside packages/inventory-manager/.

Fix: add _configPath() helper to every program that resolves config
file paths to usr/config/inventory-manager/ when running under Opus,
which lives outside the package directory and survives updates.
Falls back to the local _path() for standalone (non-Opus) use.

Updated files:
- inventoryManager.lua, manager/config.lua, inventoryClient.lua,
  inventoryWebBridge.lua, dropperController.lua, craftingTurtle.lua
- .package install script: saves configs to usr/config/inventory-manager/
- autorun/startup.lua: checks both persistent and package dirs
- startup/client.lua: uses persistent dir for .client_setup/.dropper_config
- web/server/Dockerfile: switch health check to wget (from prior fix)

web/server/Dockerfile

@@ -27,7 +27,7 @@ RUN chmod +x /usr/local/bin/docker-entrypoint.sh
 EXPOSE 3001
 
 HEALTHCHECK --interval=10s --timeout=5s --start-period=15s --retries=3 \
-  CMD wget -qO- http://localhost:3001/api/health || exit 1
+  CMD wget --spider -q http://localhost:3001/api/health || exit 1
 
 ENTRYPOINT ["docker-entrypoint.sh"]
 CMD ["node", "server.js"]