feat(tests): on-hold button with reason modal, Jira comment + On Hold transition

backend/app/schemas/test.py

@@ -141,6 +141,12 @@ class TestAssign(BaseModel):
     blue_tech_assignee: uuid.UUID | None = None
 
 
+class TestHold(BaseModel):
+    """Payload for placing a test on hold."""
+
+    reason: str
+
+
 # ── Legacy validate (kept for backwards compat) ────────────────────
 
 
@@ -232,6 +238,11 @@ class TestOut(BaseModel):
     red_tech_assignee: uuid.UUID | None = None
     blue_tech_assignee: uuid.UUID | None = None
 
+    # On-hold fields
+    is_on_hold: bool = False
+    hold_reason: str | None = None
+    held_at: datetime | None = None
+
     # Re-test fields
     retest_of: uuid.UUID | None = None
     # Assign retest_count = 0