Wire persisted multiACE configuration into printer lifecycle

[physicsG]

Tracks the next implementation slice of #1 after persisted provider configuration landed in #28.

Scope

• store/load the versioned PersistedProviderConfig through the existing per-printer configuration path rather than a parallel global store;
• automatically activate a configured multiACE Web provider when a matching machine becomes available;
• detach/reconfigure the provider when the saved configuration is disabled, removed, or changed;
• keep malformed persisted payloads fail-closed and leave the machine usable without multiACE;
• avoid duplicate provider startup across repeated discovery/settings reload events;
• add focused tests for initial activation, disabled config, malformed config, reconfiguration/replacement, and cleanup;
• document the remaining UI surface for editing connection settings and AMS refresh/status actions.

Out of scope for this slice: AMS UI controls and routing/G-code work.

Part of #1.