Show unknown nodes in a fashion similar to the web UI. Fixes #504

[ianmcorvidae]

Similar to how the web UI shows "UNK: ", this will show that under "User", and the hex ID that can be computed from that under "ID". The change to using self.nodesByNum was necessary to pull in those, since self.nodes only has nodes that have users, which excludes nodes in this particular state.

Fixes #504

[jp-bennett]

I don't have any unknown nodes to confirm, but the node list looks fine otherwise.

[ianmcorvidae]

Merged already (thanks!), but I should have included what it looks like via my own couple of 'em, so I'll still drop that here:

│  14 │ UNK: 2889340535                  │ !ac37d677 │ N/A   │ N/A        │ N/A         │ N/A        │ N/A       │ N/A             │ N/A            │ 13.25 dB  │       N/A │ 2024-03-02 11:42:26 │ 1 week ago     │
├─────┼──────────────────────────────────┼───────────┼───────┼────────────┼─────────────┼────────────┼───────────┼─────────────────┼────────────────┼───────────┼───────────┼─────────────────────┼────────────────┤
│  15 │ UNK: 2208397066                  │ !83a1770a │ N/A   │ N/A        │ N/A         │ N/A        │ 79%       │ 8.15%           │ 0.50%          │ 10.75 dB  │       N/A │ 2024-03-02 11:41:37 │ 1 week ago     │