Add Gravatar and DNS Records collectors

Two pure-PHP collectors, no Python/venv/subprocess needed:
- GravatarRunner (email): checks gravatar.com/avatar/{md5}?d=404 for a
  200 vs 404. Scoped to that binary signal since Gravatar's profile
  JSON endpoint now requires API auth even for real, public profiles
  (confirmed against Gravatar's own creator's email).
- DnsRunner (domain): dns_get_record() for A/AAAA/MX/NS/TXT/CNAME. Raw
  payload is naturally keyed by record type, which the existing
  generic list-renderer on the investigation page turns into one
  collapsible section per type with no UI changes needed.

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

app/Osint/RunnerRegistry.php

@@ -3,6 +3,8 @@
 namespace App\Osint;
 
 use App\Osint\Runners\CrtShRunner;
+use App\Osint\Runners\DnsRunner;
+use App\Osint\Runners\GravatarRunner;
 use App\Osint\Runners\HoleheRunner;
 use App\Osint\Runners\IpApiRunner;
 use App\Osint\Runners\SherlockRunner;
@@ -25,6 +27,8 @@ class RunnerRegistry
         'ip-api' => IpApiRunner::class,
         'theharvester' => TheHarvesterRunner::class,
         'holehe' => HoleheRunner::class,
+        'gravatar' => GravatarRunner::class,
+        'dns' => DnsRunner::class,
     ];
 
     public function has(string $sourceKey): bool