fix(pago): diagnose and harden IMAP email validation

- PagoValidadorService: add detailed Log::info at every step (emails count,
  body preview, parser result, which filter fails) so failures are visible in laravel.log
- CorreoImapService::cleanBody: detect and decode base64-encoded BODY[1] before
  QP decoding — critical fix when Bancolombia sends HTML part as base64
- BancolombiaParser: make esBancolombia() broader (includes 'valor','$','abono' etc.),
  add extraerPrimero() helper, add multiple regex fallbacks for remitente/fecha/hora/valor
  to handle different Bancolombia email HTML formats beyond the SMS text pattern

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

app/Services/CorreoImapService.php

@@ -304,9 +304,18 @@ class CorreoImapService
 
     private function cleanBody(string $body): string
     {
-        // ── 1. Decoded quoted-printable ──────────────────────────────────
-        // BODY.PEEK[1] retorna directamente el contenido de la parte (sin
-        // boundaries), pero puede estar codificado en quoted-printable.
+        // ── 0. Base64 — detectar antes que QP ────────────────────────────
+        // BODY[1] puede llegar codificado en base64 (Content-Transfer-Encoding: base64)
+        // si el servidor no decodifica automáticamente.
+        $noWs = preg_replace('/[\r\n\t ]/', '', $body);
+        if (strlen($noWs) > 60 && preg_match('/^[A-Za-z0-9+\/]+=*$/', $noWs)) {
+            $decoded = base64_decode($noWs, true);
+            if ($decoded !== false && preg_match('//u', $decoded)) {
+                $body = $decoded;
+            }
+        }
+
+        // ── 1. Quoted-printable ──────────────────────────────────────────
         if (preg_match('/=[0-9A-F]{2}/i', $body) || preg_match('/=\r?\n/m', $body)) {
             $body = quoted_printable_decode($body);
         }