fix(pgbouncer): PgBouncer is unreachable when the release name does not contain "flagsmith"

[germangarces]

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Changes

With PgBouncer switched on, the API never started — it could not reach PgBouncer.

The chart built PgBouncer's name in two different ways, so the address given to the API did not match the name of the PgBouncer service. They only matched when the release name contained "flagsmith", which is what our docs use, so nobody hit it.

Release name	PgBouncer service	Address given to the API
flagsmith	flagsmith-pgbouncer	flagsmith-pgbouncer	works
fs	fs-flagsmith-pgbouncer	fs-pgbouncer	broken

• Build the address the same way the service name is built.

Note for release notes: anyone who worked around this with fullnameOverride will see the address change again.

How did you test this code?

helm install fs charts/flagsmith -n test --set pgbouncer.enabled=true --wait

Before: API pod stuck retrying could not translate host name "fs-pgbouncer...".
After: install finishes, API pod 1/1 Running, PgBouncer logs show it logging in.

Also rendered four release names plus nameOverride and fullnameOverride — address matches the service every time, and the names that already worked are unchanged. helm lint passes. Kubernetes v1.35.1.

Review effort: 1/5

[matthewelwell]

How will this affect existing deployments?

[germangarces]

How will this affect existing deployments?

The host only changes where it did not match the Service, so PgBouncer was already unreachable