Add OpenCorporates collector for org targets, gated on an API token

Closes the last coverage gap for org (person remains intentionally
unaddressed — no good free/non-scraping option exists). Unlike the
other 8 sources, OpenCorporates now requires an API token even on its
free tier (confirmed: keyless request gets 401). RunnerRegistry::has()
checks services.opencorporates.token is configured before exposing the
source as runnable, so it degrades to "not yet integrated" in the UI
rather than a broken Run button, until OPENCORPORATES_API_TOKEN is set.

Also fixes a real bug hit while building this: a RunnerRegistry::REQUIRES
class constant mapping source key to a closure crashed on file load
(PHP class constants can't hold closures) — inlined the one check
instead of building an abstraction for a single case.

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

app/Providers/AppServiceProvider.php

@@ -32,5 +32,10 @@ class AppServiceProvider extends ServiceProvider
         RateLimiter::for('osint-runner:holehe', fn () => Limit::perMinute(15));
         RateLimiter::for('osint-runner:gravatar', fn () => Limit::perMinute(45));
         RateLimiter::for('osint-runner:dns', fn () => Limit::perMinute(60));
+
+        // OpenCorporates' free tier is 50 requests/day, 200/month — this
+        // matches their real quota (not a courtesy limit) to protect the
+        // configured token from getting exhausted or suspended.
+        RateLimiter::for('osint-runner:opencorporates', fn () => Limit::perDay(50));
     }
 }