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/order/a-z.svg

@@ -0,0 +1,10 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<svg width="24" height="24" viewBox="0 0 24 24"
+     xmlns="http://www.w3.org/2000/svg" role="img" aria-label="Sort A to Z">
+  <!-- Orange rounded square -->
+  <rect x="1" y="1" width="22" height="22" rx="5" fill="#F97316"/>
+  <!-- A–Z label -->
+  <text x="12" y="12" text-anchor="middle" dominant-baseline="middle"
+        font-family="system-ui, -apple-system, BlinkMacSystemFont, Segoe UI, Roboto, Arial, sans-serif"
+        font-size="9" font-weight="700" fill="#FFFFFF">A–Z</text>
+</svg>

static/order/h-l.svg

@@ -0,0 +1,10 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<svg width="24" height="24" viewBox="0 0 24 24"
+     xmlns="http://www.w3.org/2000/svg" role="img" aria-label="Sort £ hi to Lo">
+  <!-- Orange rounded square -->
+  <rect x="1" y="1" width="22" height="22" rx="5" fill="#F97316"/>
+  <!-- A–Z label -->
+  <text x="12" y="12" text-anchor="middle" dominant-baseline="middle"
+        font-family="system-ui, -apple-system, BlinkMacSystemFont, Segoe UI, Roboto, Arial, sans-serif"
+        font-size="9" font-weight="700" fill="#FFFFFF">£ ↓</text>
+</svg>

static/order/l-h.svg

@@ -0,0 +1,10 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<svg width="24" height="24" viewBox="0 0 24 24"
+     xmlns="http://www.w3.org/2000/svg" role="img" aria-label="Sort £ lo to hi">
+  <!-- Orange rounded square -->
+  <rect x="1" y="1" width="22" height="22" rx="5" fill="#F97316"/>
+  <!-- A–Z label -->
+  <text x="12" y="12" text-anchor="middle" dominant-baseline="middle"
+        font-family="system-ui, -apple-system, BlinkMacSystemFont, Segoe UI, Roboto, Arial, sans-serif"
+        font-size="9" font-weight="700" fill="#FFFFFF">£ ↑</text>
+</svg>

static/order/z-a.svg

@@ -0,0 +1,10 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<svg width="24" height="24" viewBox="0 0 24 24"
+     xmlns="http://www.w3.org/2000/svg" role="img" aria-label="Sort Z to A">
+  <!-- Orange rounded square -->
+  <rect x="1" y="1" width="22" height="22" rx="5" fill="#F97316"/>
+  <!-- A–Z label -->
+  <text x="12" y="12" text-anchor="middle" dominant-baseline="middle"
+        font-family="system-ui, -apple-system, BlinkMacSystemFont, Segoe UI, Roboto, Arial, sans-serif"
+        font-size="9" font-weight="700" fill="#FFFFFF">Z-A</text>
+</svg>