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>

suma_browser/templates/_oob_elements.html

@@ -0,0 +1,33 @@
+{% extends oob.oob_extends %}
+
+{# OOB elements for HTMX navigation - all elements that need updating #}
+
+{# Import shared OOB macros #}
+{% from '_types/root/_oob_menu.html' import mobile_menu with context %}
+
+{% block oobs %}
+
+  {% from '_types/root/_n/macros.html' import oob_header with context %}
+  {{oob_header(
+    oob.parent_id,
+    oob.child_id,
+    oob.header,
+  )}}
+
+  {% from oob.parent_header import header_row with context %}
+  {{ header_row(oob=True) }}
+{% endblock %}
+
+
+{# Mobile menu - from market/index.html _main_mobile_menu block #}
+{% set mobile_nav %}
+  {% include oob.nav %}
+{% endset %}
+{{ mobile_menu(mobile_nav) }}
+
+
+{% block content %}
+    {% include oob.main %}
+{% endblock %}
+
+