fix(manager-core): F-P-007 concurrent queue dispatch per tick

tick_queue_arm called list_active_queue_consumers() and then iterated
serially, awaiting one queue.claim(app, queue) per consumer. With N
consumers and a 100ms tick the worst-case throughput was
N × (claim + executor) / tick — one slow handler blocked every other
queue's progress on the dispatcher's task.

Replace the for-loop with `futures::stream::iter(consumers)
.for_each_concurrent(QUEUE_DISPATCH_PARALLELISM, …)`. The execution
gate already caps real script-concurrency to its permits, so this just
removes the dispatcher-side serialization.

QUEUE_DISPATCH_PARALLELISM = 32 (matches the default gate). Workspace
gains `futures = 0.3` so `for_each_concurrent` is available.

AUDIT.md anchor: F-P-007.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

crates/manager-core/Cargo.toml

@@ -14,6 +14,7 @@ picloud-executor-core.workspace = true
 picloud-orchestrator-core.workspace = true
 
 async-trait.workspace = true
+futures.workspace = true
 axum.workspace = true
 rand.workspace = true
 serde.workspace = true