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>

alembic/old_versions/1a1f1f1fc71c_merge_heads.py

@@ -0,0 +1,24 @@
+
+# Alembic migration script template
+
+"""empty message
+
+Revision ID: 1a1f1f1fc71c
+Revises: 20251107_180000_link_listings_to_nav_ids, 20251107_add_product_id_to_likes
+Create Date: 2025-11-07 19:34:18.228002
+
+"""
+from alembic import op
+import sqlalchemy as sa
+
+# revision identifiers, used by Alembic.
+revision = '1a1f1f1fc71c'
+down_revision = ('20251107_180000_link_listings_to_nav_ids', '20251107_add_product_id_to_likes')
+branch_labels = None
+depends_on = None
+
+def upgrade() -> None:
+    pass
+
+def downgrade() -> None:
+    pass