fix(labs): synchronous confirm transaction — async callback broke atomicity

bun-sqlite's Database.transaction is synchronous, but async callbacks return
a pending Promise at the first await, causing immediate COMMIT before the
entire callback completes. This allowed partial inserts with no rollback.

Fixed by:
- Remove async from transaction callback
- Add .run() to each insert/update to execute synchronously
- Add regression test proving atomicity: transaction that throws mid-loop
  rolls back all changes (both tables empty after failure)

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

server/src/routes/labs.ts

@@ -87,19 +87,19 @@ export function labsRoutes(deps: LabsDeps) {
       panel: m.panel, name: m.name, value: m.value, unit: m.unit,
       referenceRange: m.referenceRange, flagged: m.flagged,
     }));
-    await deps.db.transaction(async (tx) => {
-      await tx.insert(labDraws).values({
+    deps.db.transaction((tx) => {
+      tx.insert(labDraws).values({
         id: drawId, collectedAt: body.data.collectedDate, labName: body.data.labName,
         draftId: row.id, createdAt: Date.now(),
-      });
+      }).run();
       for (const n of norm) {
-        await tx.insert(biomarkers).values({
+        tx.insert(biomarkers).values({
           drawId, panel: n.panel, name: n.name, marker: n.marker, analyteKey: n.analyteKey,
           value: n.value, valueNum: n.valueNum, unit: n.unit, referenceRange: n.referenceRange,
           flagged: n.flagged ? 1 : 0, valueCanonical: n.valueCanonical, canonicalUnit: n.canonicalUnit,
-        });
+        }).run();
       }
-      await tx.update(labDrafts).set({ status: "confirmed" }).where(eq(labDrafts.id, row.id));
+      tx.update(labDrafts).set({ status: "confirmed" }).where(eq(labDrafts.id, row.id)).run();
     });
     return c.json({ drawId }, 201);
   });