feat(dv-pod): add fetchFeeRecipientUpdates charon flag

[nickh-obol]

Summary

• Adds a new charon.fetchFeeRecipientUpdates helm value (defaults to true) that renders the charon --fetch-feerecipient-updates CLI flag on the main charon container.
• When enabled, charon polls the Obol API for signed fee recipient update messages that override the currently configured fee recipient. Charon's own default for this flag is false, so this chart default flips it on.
• Flag is rendered unconditionally so users who set the value to false still get --fetch-feerecipient-updates=false passed explicitly.

Test plan

• helm lint charts/dv-pod passes
• helm template renders --fetch-feerecipient-updates=true by default
• helm template --set charon.fetchFeeRecipientUpdates=false renders --fetch-feerecipient-updates=false
• make docs regenerated charts/dv-pod/README.md cleanly
• Deploy a dv-pod with the new default and confirm charon starts with the flag enabled

[nickh-obol]

Blocked on charon v1.10.0 stable release

Converting to draft — the --fetch-feerecipient-updates flag is not present in charon v1.9.x (the chart's currently-pinned default). It was introduced in v1.10.0-rc5.

Before this can merge:

• charon v1.10.0 stable is released
• Bump image.tag default in values.yaml to v1.10.0
• Bump appVersion in Chart.yaml to 1.10.0
• Re-run make docs

Without the charon bump, any default helm install would crash-loop on an unknown flag.