Jul 7 - Implement QR codes for facility

migrations/versions/phase38_facility_qr.py

@@ -0,0 +1,58 @@
+"""phase38 — facility QR tokens
+
+Adds facilities.qr_token VARCHAR(64) NULL + unique index. The token backs the
+public, login-less facility QR scan page (GET /f/<token>) which shows recent
+inspection scores, open-issue counts, and a 30-day score trend for that
+facility — counts + scores only, no free text, no names, no photos.
+
+NULL for all existing rows; Facility.ensure_qr_token() generates lazily when
+staff first open the QR card / bulk sheet.
+
+Idempotent: INFORMATION_SCHEMA column + index existence checks — safe to
+re-run across every tenant DB (CLAUDE.md rule 14). Revision id kept ≤ 32
+chars (alembic_version.version_num is VARCHAR(32)).
+"""
+
+import sqlalchemy as sa
+from alembic import op
+
+revision      = 'phase38_facility_qr'
+down_revision = 'phase37_contract_recipients'
+branch_labels = None
+depends_on    = None
+
+
+def _column_exists(bind, table: str, column: str) -> bool:
+    result = bind.execute(sa.text(
+        "SELECT COUNT(*) FROM information_schema.columns "
+        "WHERE table_schema = DATABASE() AND table_name = :t AND column_name = :c"
+    ), {'t': table, 'c': column})
+    return result.scalar() > 0
+
+
+def _index_exists(bind, table: str, index: str) -> bool:
+    result = bind.execute(sa.text(
+        "SELECT COUNT(*) FROM information_schema.statistics "
+        "WHERE table_schema = DATABASE() AND table_name = :t AND index_name = :i"
+    ), {'t': table, 'i': index})
+    return result.scalar() > 0
+
+
+def upgrade():
+    bind = op.get_bind()
+    if not _column_exists(bind, 'facilities', 'qr_token'):
+        op.execute(sa.text(
+            "ALTER TABLE facilities ADD COLUMN qr_token VARCHAR(64) NULL"
+        ))
+    if not _index_exists(bind, 'facilities', 'uq_facilities_qr_token'):
+        op.execute(sa.text(
+            "CREATE UNIQUE INDEX uq_facilities_qr_token ON facilities (qr_token)"
+        ))
+
+
+def downgrade():
+    bind = op.get_bind()
+    if _index_exists(bind, 'facilities', 'uq_facilities_qr_token'):
+        op.execute(sa.text('DROP INDEX uq_facilities_qr_token ON facilities'))
+    if _column_exists(bind, 'facilities', 'qr_token'):
+        op.execute(sa.text('ALTER TABLE facilities DROP COLUMN qr_token'))