Block manual send reservation for unreleased shared numbers

Implement shared-number detection in reserveOutreachSend: reject manual WhatsApp sends with HTTP 409 when the destination number is shared across 2+ leads and hasn't been explicitly released via override.

- Add test: reserveOutreachSend bloqueia numero compartilhado sem override e libera com override
- Add check in reserveOutreachSend right after isOptedOut check
- Uses isNumberSharedAcrossLeads and isSharedNumberOverridden from Task 1

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

tests/db.test.mjs

@@ -501,6 +501,23 @@ test('limite manual e uso publicado compartilham origem e status exatos', () =>
   db.close();
 });
 
+test('reserveOutreachSend bloqueia numero compartilhado sem override e libera com override', () => {
+  const db = openDb(':memory:');
+  const insert = createLeadInserter(db);
+  insert(sampleLead({ dedup_key: 'shared-a', empresa: 'Empresa A', whatsapp: '5511999990009' }));
+  insert(sampleLead({ dedup_key: 'shared-b', empresa: 'Empresa B', whatsapp: '5511999990009' }));
+
+  assert.throws(
+    () => reserveOutreachSend(db, { numero: '5511999990009', mensagem: 'oi' }),
+    (error) => error.statusCode === 409
+  );
+
+  database.addSharedNumberOverride(db, '5511999990009', 'liberado');
+  const sendId = reserveOutreachSend(db, { numero: '5511999990009', mensagem: 'oi' });
+  assert.ok(sendId > 0);
+  db.close();
+});
+
 test('cache de verificacao salva somente o numero solicitado e consulta equivalentes', () => {
   const db = openDb(':memory:');
   const tables = db.prepare("SELECT name FROM sqlite_master WHERE type='table'").all().map((row) => row.name);