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>

docker-compose.yml

@@ -8,6 +8,7 @@ services:
     environment:
       - ORIGIN=${PLATFORM_V2_ORIGIN:-https://dash.quadjourney.com}
       - GATEWAY_URL=http://gateway:8100
+      - DEV_AUTO_LOGIN=${DEV_AUTO_LOGIN:-0}
       - IMMICH_URL=${IMMICH_URL}
       - IMMICH_API_KEY=${IMMICH_API_KEY}
       - KARAKEEP_URL=${KARAKEEP_URL:-http://192.168.1.42:3005}
@@ -35,6 +36,9 @@ services:
       - ADMIN_USERNAME=${ADMIN_USERNAME}
       - ADMIN_PASSWORD=${ADMIN_PASSWORD}
       - ADMIN_DISPLAY_NAME=${ADMIN_DISPLAY_NAME:-Admin}
+      - DEV_AUTO_LOGIN=${DEV_AUTO_LOGIN:-0}
+      - DEV_AUTO_LOGIN_USERNAME=${DEV_AUTO_LOGIN_USERNAME:-dev}
+      - DEV_AUTO_LOGIN_DISPLAY_NAME=${DEV_AUTO_LOGIN_DISPLAY_NAME:-Dev User}
       - PORT=8100
       - TRIPS_BACKEND_URL=http://trips-service:8087
       - FITNESS_BACKEND_URL=http://fitness-service:8095