feat(cluster): record frontend replicas in a shared instances table

Replicas need to find each other to relay worker traffic, and nothing in
the tree recorded a replica's address. The advertised address is discovered
by opening a UDP socket toward PostgreSQL and reading back the local
address, which yields the interface every replica demonstrably shares
without asking an operator to configure one.

Assisted-by: Claude Opus 5 [claude-code]
Signed-off-by: Ettore Di Giacinto <mudler@localai.io>
This commit is contained in:
Internal Server Error - Gitea: Git with a cup of tea
500 Internal Server Error

Gitea Version: 1.28.0+dev-477-g8b6ad49a5f