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/versions/0001_initial_schem.py

@@ -0,0 +1,33 @@
+"""Initial database schema from schema.sql"""
+
+from alembic import op
+import sqlalchemy as sa
+import pathlib
+
+# revision identifiers, used by Alembic
+revision = '0001_initial_schema'
+down_revision = None
+branch_labels = None
+depends_on = None
+
+def upgrade():
+    return
+    schema_path = pathlib.Path(__file__).parent.parent.parent / "schema.sql"
+    with open(schema_path, encoding="utf-8") as f:
+        sql = f.read()
+    conn = op.get_bind()
+    conn.execute(sa.text(sql))
+
+def downgrade():
+    return
+    # Drop all user-defined tables in the 'public' schema
+    conn = op.get_bind()
+    conn.execute(sa.text("""
+        DO $$ DECLARE
+            r RECORD;
+        BEGIN
+            FOR r IN (SELECT tablename FROM pg_tables WHERE schemaname = 'public') LOOP
+                EXECUTE 'DROP TABLE IF EXISTS public.' || quote_ident(r.tablename) || ' CASCADE';
+            END LOOP;
+        END $$;
+    """))