Resolve the extension's localhost-reachability gap

[JSONbored]

Problem: The extension's manifest host_permissions only cover github.com — it architecturally cannot reach localhost as currently scoped, which blocks any live-fetch integration with the local miner-ui.

Area: AMS / Extension

Proposal: Add the necessary host permission (scoped as narrowly as the platform allows, e.g. a specific localhost port) to the manifest.

Deliverables:

• Updated manifest permissions enabling localhost access.

Acceptance criteria:

• The extension can successfully fetch from the local miner-ui API after this change.

[linear-code]

JSO-3520