Fix software-compliance report + relationshiptypes zero-dates

- Add applications.isrequired (model + migration 7c02 + create/update + form
  checkbox). The software-compliance report compared required apps against
  installs but no such flag existed, so it 500'd; now it works.
- Repair relationshiptypes rows with 0000-00-00 createddate/modifieddate
  (partof/connectedto) to real timestamps.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

migrations/versions/7c02_application_isrequired.py

@@ -0,0 +1,29 @@
+"""Add applications.isrequired
+
+Backs the software-compliance report, which compares required applications
+against what is installed per PC. There was no such flag before, so the report
+errored.
+
+Revision ID: 7c02_app_isrequired
+Revises: 7c01_drop_legacy_machine
+Create Date: 2026-06-26
+
+"""
+from alembic import op
+import sqlalchemy as sa
+
+
+revision = '7c02_app_isrequired'
+down_revision = '7c01_drop_legacy_machine'
+branch_labels = None
+depends_on = None
+
+
+def upgrade():
+    op.add_column('applications', sa.Column(
+        'isrequired', sa.Boolean(), nullable=True, server_default=sa.false(),
+        comment='Required on all PCs (drives the software-compliance report)'))
+
+
+def downgrade():
+    op.drop_column('applications', 'isrequired')