feat(tests): disputed state + fix timestamps on reopen

1. New 'disputed' state — one lead approved, the other rejected:
   - Both approved → validated (unchanged)
   - Both rejected → rejected (unchanged)
   - One approves + one rejects → disputed (new)
   - DB: ALTER TYPE teststate ADD VALUE 'disputed'
   - Notification sent to the approving lead explaining the conflict
     with the rejection notes

2. Disputed UI in TestDetailHeader:
   - Amber banner showing conflict + rejection reason from notes
   - 'Change Vote to Rejected' button for the lead who approved
   - Validation indicators shown for disputed state too

3. Fix timestamps on reopen (rejected → draft):
   - Keep red_started_at, blue_started_at etc. as historical record
   - Only clear paused_at defensively
   - Timestamps naturally update when test is re-executed

4. disputed badge (amber) added to all badge color maps

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

backend/alembic/versions/b046_add_disputed_test_state.py

@@ -0,0 +1,22 @@
+"""Add 'disputed' value to teststate enum.
+
+Revision ID: b046
+Revises: b045
+Create Date: 2026-06-03
+"""
+
+from alembic import op
+
+revision = "b046"
+down_revision = "b045"
+branch_labels = None
+depends_on = None
+
+
+def upgrade() -> None:
+    op.execute("ALTER TYPE teststate ADD VALUE IF NOT EXISTS 'disputed'")
+
+
+def downgrade() -> None:
+    # PostgreSQL does not support removing enum values; downgrade is a no-op.
+    pass