Initial implementation: multi-tenant Kanban board (Phase 1)

Complete Phase 1 foundation with working board, column, and card CRUD:
- SvelteKit + TypeScript + Tailwind CSS v4 + adapter-node
- Full Prisma schema with 18 tables (tenants, users, boards, columns, cards, etc.)
- Multi-tenant architecture with hostname-based tenant resolution
- Email/password auth with bcrypt + session cookies
- Board/Column/Card API routes with full CRUD
- Fractional indexing for drag-and-drop ordering
- Board view with svelte-dnd-action for column and card drag-and-drop
- Card modal with inline editing
- Auth pages (login, register)
- Board listing with create form
- RLS policies SQL script for tenant isolation
- Prisma RLS client extensions (forTenant/bypassRLS)
- Permission helpers (canEditBoard, canManageMembers, etc.)
- Socket.IO server setup (dev Vite plugin + production Express server)
- Client-side socket store for real-time updates
- Docker Compose (app + PostgreSQL 16) + multi-stage Dockerfile
- Database seed script (default tenant + admin user)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

docker-compose.yml

@@ -0,0 +1,38 @@
+services:
+  db:
+    image: postgres:16-alpine
+    restart: unless-stopped
+    environment:
+      POSTGRES_USER: kanban
+      POSTGRES_PASSWORD: kanban
+      POSTGRES_DB: kanban
+    ports:
+      - '5432:5432'
+    volumes:
+      - pgdata:/var/lib/postgresql/data
+    healthcheck:
+      test: ['CMD-SHELL', 'pg_isready -U kanban']
+      interval: 5s
+      timeout: 5s
+      retries: 5
+
+  app:
+    build: .
+    restart: unless-stopped
+    ports:
+      - '3000:3000'
+    environment:
+      DATABASE_URL: postgresql://kanban:kanban@db:5432/kanban?schema=public
+      SESSION_SECRET: ${SESSION_SECRET:-change-me-in-production}
+      ORIGIN: ${ORIGIN:-http://localhost:3000}
+      PORT: 3000
+      HOST: 0.0.0.0
+    depends_on:
+      db:
+        condition: service_healthy
+    volumes:
+      - uploads:/app/uploads
+
+volumes:
+  pgdata:
+  uploads: