Fix guardian relationship_type CHECK violation — use 'father' instead of invalid 'guardian'

The guardians_relationship_type_check constraint allows: father, mother,
grandfather, grandmother, uncle, aunt, sibling, legal_guardian, other.
The ParticipantForm was inserting 'guardian' which isn't a valid value.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

app/Livewire/Participants/ParticipantForm.php

@@ -217,7 +217,7 @@ public function save(ParticipantService $service): void
                     $newGuardian = Guardian::create([
                         'academy_id' => $this->participant->academy_id,
                         'person_id' => $guardianPerson->id,
-                        'relationship_type' => 'guardian',
+                        'relationship_type' => 'father',
                         'is_emergency_contact' => true,
                         'is_financial_responsible' => true,
                         'can_pickup' => true,