feat: brain service — self-contained second brain knowledge manager

Full backend service with:
- FastAPI REST API with CRUD, search, reprocess endpoints
- PostgreSQL + pgvector for items and semantic search
- Redis + RQ for background job processing
- Meilisearch for fast keyword/filter search
- Browserless/Chrome for JS rendering and screenshots
- OpenAI structured output for AI classification
- Local file storage with S3-ready abstraction
- Gateway auth via X-Gateway-User-Id header
- Own docker-compose stack (6 containers)

Classification: fixed folders (Home/Family/Work/Travel/Knowledge/Faith/Projects)
and fixed tags (28 predefined). AI assigns exactly 1 folder, 2-3 tags, title,
summary, and confidence score per item.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

frontend-v2/src/routes/(app)/trips/trip/+page.svelte

@@ -1,10 +1,13 @@
 <script lang="ts">
   import { onMount } from 'svelte';
   import { page } from '$app/state';
+  import AtelierTripDetailPage from '$lib/pages/trips/AtelierTripDetailPage.svelte';
   import ItemModal from '$lib/components/trips/ItemModal.svelte';
   import TripEditModal from '$lib/components/trips/TripEditModal.svelte';
   import ImageUpload from '$lib/components/trips/ImageUpload.svelte';
 
+  let { data } = $props();
+
   // ── Types ──
   interface ItineraryEvent {
     time: string; name: string; description: string;
@@ -387,6 +390,9 @@
   });
 </script>
 
+{#if data?.useAtelierShell}
+  <AtelierTripDetailPage />
+{:else}
 <div class="page trip-detail-page">
   <div class="app-surface">
     <!-- Back (hidden in share mode) -->
@@ -1039,3 +1045,4 @@
     .day-story { margin: 6px 0 4px; padding: 10px 14px; }
   }
 </style>
+{/if}