Move fleet retention and concurrency controls into Settings

Persist settings in SQLite, import legacy environment values once, and apply changes to cleanup and deployment queues without restarting.

Closes #51

src/lib/server/fleet/collections.ts

@@ -1,3 +1,4 @@
+import { fleetSettings } from '../settings.js';
 import { randomUUID } from 'node:crypto';
 import type { CollectionDetail, CollectionMode, CollectionPreview, CollectionSummary } from '$lib/deployment-plan.js';
 import { db } from '../db/index.js';
@@ -106,7 +107,7 @@ export function previewCollection(blueprintId: unknown, mode: unknown = 'fill'):
         db().prepare('DELETE FROM server_collection_previews WHERE expires_at < ? AND collection_id IS NULL').run(new Date().toISOString());
         db().prepare('INSERT INTO server_collection_previews (id, expires_at, blueprint_name, entries, servers, mode, fleet_snapshot) VALUES (?, ?, ?, ?, ?, ?, ?)')
             .run(id, expiresAt, blueprintName, JSON.stringify(entries), JSON.stringify(servers), mode, mode === 'exact' ? JSON.stringify(fleetSnapshot()) : null);
-        return { id, expiresAt, blueprintName, mode, retainedServers, removals, launchConcurrency: config.createConcurrency, servers, blockers, ready: blockers.length === 0,
+        return { id, expiresAt, blueprintName, mode, retainedServers, removals, launchConcurrency: fleetSettings().createConcurrency, servers, blockers, ready: blockers.length === 0,
             entries: entries.map((entry, index) => ({ count: entry.count, ...counts[index], recipe: summarizeRecipe(entry.recipe) })) };
     })();
 }
@@ -216,6 +217,6 @@ export function getCollection(id: string): CollectionDetail | null {
     const queue = creationQueue();
     const positions = new Map(queue.queued.map((job, index) => [job.id, index + 1]));
     const stored = db().prepare('SELECT retained_servers FROM server_launch_collections WHERE id = ?').get(id) as { retained_servers: string };
-    return { collection, retainedServers: JSON.parse(stored.retained_servers), queue: { concurrency: config.createConcurrency, active: queue.active, queued: queue.queued.length },
+    return { collection, retainedServers: JSON.parse(stored.retained_servers), queue: { concurrency: fleetSettings().createConcurrency, active: queue.active, queued: queue.queued.length },
         servers: servers.map(server => ({ ...server, queuePosition: positions.get(server.id) ?? null })) };
 }