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/remove_product_slug_20251107.py

@@ -0,0 +1,29 @@
+"""Remove product_slug from product_likes
+
+Revision ID: remove_product_slug_20251107
+Revises: 0d767ad92dd7
+Create Date: 2025-11-07
+
+"""
+from alembic import op
+import sqlalchemy as sa
+
+# revision identifiers, used by Alembic.
+revision = 'remove_product_slug_20251107'
+down_revision = '20251107_add_missing_indexes'
+branch_labels = None
+depends_on = None
+
+
+def upgrade() -> None:
+    with op.batch_alter_table("product_likes") as batch_op:
+        batch_op.drop_column("product_slug")
+
+
+def downgrade() -> None:
+    with op.batch_alter_table("product_likes") as batch_op:
+        batch_op.add_column(sa.Column(
+            "product_slug",
+            sa.String(length=255),
+            nullable=False,
+        ))