[Availability] Increase replicas and add PodAffinity defn

[siddimore]

PR Description:

Default replicaCount: 1 means a single pod failure takes out the entire service. This bumps the default to 2 replicas across livekit-server, egress, and ingress, and adds soft pod anti-affinity rules to spread them across nodes.

Changes

• Default replicaCount set to 2 for all three charts and sample files
• Added preferredDuringSchedulingIgnoredDuringExecution pod anti-affinity on each chart, matching on app.kubernetes.io/name with topologyKey: kubernetes.io/hostname

Why soft anti-affinity?
Using preferred instead of required so clusters with fewer nodes than replicas still work — the scheduler will try to spread but won't block pods from starting. For livekit-server and ingress (which use host networking), port conflicts already physically prevent two pods on the same node, but the anti-affinity makes the intent explicit.

Notes
Fully backwards compatible — users can override affinity and replicaCount as before.