Add shared-number detection and override data layer

- Add migration v19: creates outreach_shared_number_overrides table
- Implement 7 new data-layer functions:
  - leadsSharingNumber: find leads sharing a phone number variant
  - isNumberSharedAcrossLeads: detect if number is shared by 2+ leads
  - getSharedNumberOverride: retrieve override entry for a number
  - isSharedNumberOverridden: check if number has an override
  - addSharedNumberOverride: create or update override with reason
  - removeSharedNumberOverride: delete override record
  - listSharedNumberGroups: group leads by shared numbers, reflect override state
- Add 4 comprehensive tests covering migration, detection, override crud, and grouping
- Update version assertions from 18 to 19
- Fix v17 migration test to properly clean up v19 table for schema reset

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

src/db.mjs

@@ -643,6 +643,16 @@ const MIGRATIONS = [
   BEGIN
     SELECT RAISE(ABORT, 'transicao de status da fila invalida');
   END;
+  `,
+  // v19 - numeros compartilhados por mais de um lead (ex.: contabilidade que
+  // registra o proprio telefone para varios CNPJs de clientes) podem ser
+  // liberados manualmente apos revisao, revertendo o bloqueio automatico.
+  `
+  CREATE TABLE outreach_shared_number_overrides (
+    numero     TEXT PRIMARY KEY,
+    motivo     TEXT NOT NULL DEFAULT '',
+    created_at TEXT NOT NULL DEFAULT (datetime('now'))
+  );
   `
 ];
 
@@ -946,6 +956,72 @@ export function removeOptOut(db, numero) {
   });
 }
 
+export function leadsSharingNumber(db, numero) {
+  const numbers = equivalentPhoneNumbers(numero);
+  if (!numbers.length) return [];
+  const placeholders = numbers.map(() => '?').join(', ');
+  return db.prepare(`SELECT id, empresa, cnpj FROM leads WHERE whatsapp IN (${placeholders})`).all(...numbers);
+}
+
+export function isNumberSharedAcrossLeads(db, numero) {
+  return leadsSharingNumber(db, numero).length >= 2;
+}
+
+export function getSharedNumberOverride(db, numero) {
+  const numbers = equivalentPhoneNumbers(numero);
+  if (!numbers.length) return null;
+  const placeholders = numbers.map(() => '?').join(', ');
+  return db.prepare(
+    `SELECT numero, motivo, created_at FROM outreach_shared_number_overrides WHERE numero IN (${placeholders})`
+  ).get(...numbers) || null;
+}
+
+export function isSharedNumberOverridden(db, numero) {
+  return Boolean(getSharedNumberOverride(db, numero));
+}
+
+export function addSharedNumberOverride(db, numero, motivo = '') {
+  const numbers = equivalentPhoneNumbers(numero);
+  if (!numbers.length) throw new Error('numero obrigatorio');
+  return transaction(db, () => {
+    const placeholders = numbers.map(() => '?').join(', ');
+    db.prepare(`DELETE FROM outreach_shared_number_overrides WHERE numero IN (${placeholders})`).run(...numbers);
+    db.prepare('INSERT INTO outreach_shared_number_overrides (numero, motivo) VALUES (?, ?)')
+      .run(numbers[0], String(motivo || '').trim());
+    return db.prepare(
+      'SELECT numero, motivo, created_at FROM outreach_shared_number_overrides WHERE numero = ?'
+    ).get(numbers[0]);
+  });
+}
+
+export function removeSharedNumberOverride(db, numero) {
+  const numbers = equivalentPhoneNumbers(numero);
+  if (!numbers.length) return false;
+  return transaction(db, () => {
+    const placeholders = numbers.map(() => '?').join(', ');
+    return db.prepare(`DELETE FROM outreach_shared_number_overrides WHERE numero IN (${placeholders})`).run(...numbers).changes > 0;
+  });
+}
+
+export function listSharedNumberGroups(db) {
+  const rows = db.prepare("SELECT id, empresa, cnpj, whatsapp FROM leads WHERE whatsapp <> ''").all();
+  const groups = new Map();
+  for (const row of rows) {
+    const equivalents = equivalentPhoneNumbers(row.whatsapp);
+    if (!equivalents.length) continue;
+    const key = equivalents.slice().sort().join(':');
+    if (!groups.has(key)) groups.set(key, { numero: equivalents[0], leads: [] });
+    groups.get(key).leads.push({ id: row.id, empresa: row.empresa, cnpj: row.cnpj });
+  }
+  return [...groups.values()]
+    .filter((group) => group.leads.length >= 2)
+    .map((group) => {
+      const override = getSharedNumberOverride(db, group.numero);
+      return { ...group, liberado: Boolean(override), motivo: override?.motivo || null };
+    })
+    .sort((a, b) => b.leads.length - a.leads.length || a.numero.localeCompare(b.numero));
+}
+
 export function saveWhatsAppVerification(db, result) {
   const numero = normalizePhone(result?.numero);
   if (!numero) throw new Error('numero obrigatorio');