Add configurable retention for successful routine operations

src/routes/settings/+page.svelte

@@ -54,6 +54,9 @@
                     <label for="retention">Campaign history retention (days)</label>
                     <input id="retention" type="number" min="1" max="36500" step="1" required bind:value={settings.deployKeepDays} aria-describedby="retention-help" />
                     <p id="retention-help">Default: 7 days. Removes eligible old campaign records and file diffs on the next cleanup check. Pending, failed, held, and health-recovery-linked campaigns are kept. Provisioning history is retained.</p>
+                    <label for="observation-retention">Routine operation history retention (days)</label>
+                    <input id="observation-retention" type="number" min="0" max="36500" step="1" required bind:value={settings.observationKeepDays} aria-describedby="observation-retention-help" />
+                    <p id="observation-retention-help">Default: 1 day. Removes successful monitoring and file-read operation records on the next cleanup check. Failures and actions are retained. Set to 0 to keep these records indefinitely.</p>
                     <label for="restarts">Concurrent restarts</label>
                     <input id="restarts" type="number" min="1" step="1" required bind:value={settings.restartConcurrency} aria-describedby="restarts-help" />
                     <p id="restarts-help">Default: 1 across the fleet. Campaigns, betas, maintenance, and lifecycle actions share recovery slots until container and game health are verified.</p>