feat: complete person identity matching system with fuzzy detection, revert, and manual link

Implements the full identity matching engine: email matching (HIGH confidence),
fuzzy name matching with Levenshtein distance (MEDIUM confidence, upgradable to
HIGH with DOB tiebreaker), manual link/unlink, revert confirmed matches, and
automatic detection via PersonObserver. Includes 33 comprehensive tests, frontend
integration with confirm/dismiss/unlink UI, and match indicators in the persons list.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

api/app/Http/Resources/Api/V1/MeResource.php

@@ -17,6 +17,7 @@ final class MeResource extends JsonResource
             'first_name' => $this->first_name,
             'last_name' => $this->last_name,
             'full_name' => $this->full_name,
+            'date_of_birth' => $this->date_of_birth?->toDateString(),
             'email' => $this->email,
             'timezone' => $this->timezone,
             'locale' => $this->locale,