Add configurable history and storage retention policies

src/routes/campaigns/[id]/+page.svelte

@@ -31,6 +31,7 @@
         attempts: number; error: string | null;
     }
     interface Detail {
+        fileContentsExpired?: boolean;
         deployment: {
             id: string; action: string; started_at: string;
             finished_at: string | null; triggered_by: string | null; beta_id?: number | null;
@@ -96,7 +97,7 @@
         diffOpen = true; diffLoading = true; diffError = ''; openFile = null;
         try {
             const response = await fetch('/api/campaigns/' + id + '/file/' + f.id);
-            if (!response.ok) throw new Error('Could not load this file comparison. Close and select it again to retry.');
+            if (!response.ok) throw new Error(response.status === 410 ? 'File contents expired under the retention policy.' : 'Could not load this file comparison. Close and select it again to retry.');
             const body = await response.json();
             if (id === $page.params.id && current === diffRequest) openFile = {id:f.id, ...body};
         } catch (error) { if (id === $page.params.id && current === diffRequest) diffError = (error as Error).message; }
@@ -139,6 +140,7 @@
             {/snippet}
         </SectionHeader>
     <BackLink fallback="/campaigns" />
+        {#if detail.fileContentsExpired}<p role="status">File contents have expired under the retention policy. File comparisons and rollback are unavailable.</p>{/if}
 
         <section class="outcome" aria-label="Campaign outcome">
             <h2>{completed} / {detail.servers.length} servers activated{unresolved ? ` · ${unresolved} unresolved` : ''}{withdrawn ? ` · ${withdrawn} withdrawn` : ''}{deletedIncomplete ? ` · ${deletedIncomplete} deleted before activation` : ''}</h2>
@@ -209,7 +211,7 @@
                         <h3><HistoricalServerIdentity name={srv} deletedAt={detail.servers.find(server => server.server === srv)?.server_deleted_at} /></h3>
                         <div class="file-rows">
                             {#each files as f (f.id)}
-                                <button class="file-row" onclick={() => loadDiff(f)}>
+                                <button class="file-row" disabled={detail.fileContentsExpired} onclick={() => loadDiff(f)}>
                                     <Badge variant={verbVariant(f.verb)} size="sm" uppercase>{f.verb}</Badge>
                                     {#if f.apply_state !== 'applied'}<Badge variant="neutral" size="sm">{f.apply_state === 'pending' ? 'Queued' : f.apply_state === 'applying' ? 'Needs inspection' : 'Cancelled'}</Badge>{/if}
                                     <span class="path">{f.rel_path}</span>