[feature] Allow to easily find out the device linked to a specific IP Address

[nemesifier]

We need to find a way to easily show to which device IP addresses and subnets are linked to.
We also need to find a way to show this via the API.

[xoaryaa]

hey @nemesifier id like to work on this

Idea: add a simple “reverse lookup” so users can type an IP (or CIDR) and quickly see which device/config it belongs to both in the admin UI and via the API.

UI

• In IpAddress admin: show a readonly “linked device” field (and ideally a column in the list view too).
• In Subnet admin: show “linked devices” as a count + link to the filtered device list.

API

Add a small endpoint in controller (since “device” is a controller concept), e.g.

• GET /api/v1/controller/device/lookup-ip/?ip=...
• GET /api/v1/controller/device/lookup-subnet/?subnet=...

return a compact payload with device_id/name, config_id, and the matching ipaddress_id/subnet_id (+ org/rule ids if helpful).

Implementation

rather than guessing from labels/descriptions, id add a tiny index table that stores the mapping when subnet-division provisioning happens:

• ipaddress -> config/device (+ org, rule)
• subnet -> config/device (+ org, rule)
  with DB indexes on (org, ip) and (org, subnet).

happy to start with backend and then wire up the admin UI if this direction sounds good.