feat: initial shared library extraction

Contains shared infrastructure for all coop services:
- shared/ (factory, urls, user_loader, context, internal_api, jinja_setup)
- models/ (User, Order, Calendar, Ticket, Product, Ghost CMS)
- db/ (SQLAlchemy async session, base)
- suma_browser/app/ (csrf, middleware, errors, authz, redis_cacher, payments, filters, utils)
- suma_browser/templates/ (shared base layouts, macros, error pages)
- static/ (CSS, JS, fonts, images)
- alembic/ (database migrations)
- config/ (app-config.yaml)
- editor/ (Lexical editor Node.js build)
- requirements.txt

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

editor/package.json

@@ -0,0 +1,18 @@
+{
+  "name": "coop-lexical-editor",
+  "version": "2.0.0",
+  "private": true,
+  "scripts": {
+    "build": "node build.mjs",
+    "build:prod": "NODE_ENV=production node build.mjs",
+    "dev": "node build.mjs --watch"
+  },
+  "dependencies": {
+    "@tryghost/koenig-lexical": "^1.7.10",
+    "react": "^18.3.1",
+    "react-dom": "^18.3.1"
+  },
+  "devDependencies": {
+    "esbuild": "^0.24.0"
+  }
+}