Finish the plugin RPC decorator rollout

The last 20 wire methods move onto the decorators: db.* and the three
unconditional methods (DbRpc), meta.* (MetaRpc) and the host-mediated surface
of users/broadcasts/notify/ai/oauth/scheduler (HostSurfaceRpc). That closes the
ledger at 113/113, so the legacy has() blocks in rpc-host.ts are gone and the
router is down to what was never domain-specific: build the granted subset of
the dispatch map, dispatch, audit, map errors.

PluginHostDepsFactory was the 26-argument wiring sheet behind those blocks. With
the handlers in the domains it has two dependencies left, so it is now
PluginRpcHostFactory: the plugin's own sqlite handle, the inter-plugin router
bound with this plugin as the caller, and the audit sink.

The 18 host-to-plugin hook calls get the same treatment. They used to spell out
the fn name and the timeout at each controller, which meant nothing checked that
a hook:* grant on the consent screen had a consumer behind it, that the fn
matched what the SDK documents, or that two call sites agreed on the budget.
PluginHooks declares all 18 with @PluginHook and performs them, and the
controllers call it by name.

With both halves complete, requireTotalCoverage goes on: a KNOWN_METHOD without
a handler, or a hook without a consumer, now fails app boot instead of surfacing
as a PERMISSION_DENIED nobody can explain.

server/src/nest/notifications/notifications.module.ts

@@ -14,7 +14,7 @@ import { AuthModule } from '../auth/auth.module';
  *  mail without AuthModule and NotificationsModule importing each other.
  *  NotificationsService and NotificationPreferencesService are exported for
  *  in-container consumers (AdminController's dev test send and preferences tab,
- *  the plugin RPC host's PluginHostDepsFactory). */
+ *  the plugin RPC surface, HostSurfaceRpc). */
 @Module({
   imports: [AuthModule, MailerModule],
   controllers: [NotificationsController],