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>

static/styles/basics.css

@@ -0,0 +1,32 @@
+:root {
+    --brand-color: var(--ghost-accent-color, #ff572f);
+    --primary-text-color: #333;
+    --secondary-text-color: #999;
+    --white-color: #fff;
+    --lighter-gray-color: #f6f6f6;
+    --light-gray-color: #e6e6e6;
+    --mid-gray-color: #ccc;
+    --dark-gray-color: #444;
+    --darker-gray-color: #1a1a1a;
+    --black-color: #000;
+    --green-color: #28a745;
+    --orange-color: #ffc107;
+    --red-color: #dc3545;
+    --facebook-color: #3b5998;
+    --twitter-color: #1da1f2;
+    --rss-color: #f26522;
+    --animation-base: ease-in-out;
+    --font-sans: Mulish, -apple-system, BlinkMacSystemFont, Segoe UI, Helvetica, Arial, sans-serif;
+    --font-serif: Lora, Times, serif;
+    --navbar-height: 80px;
+    --content-font-size: 1.7rem;
+    --header-spacing: 6vmin;
+}
+
+.is-head-brand {
+    --header-spacing: 8vmin;
+}
+
+:where(h1, h2, h3, h4, h5, h6) {
+    font-weight: 800;
+}