Rebrand from MyCrib to Casera

- Update Go module from mycrib-api to casera-api
- Update all import statements across 69 Go files
- Update admin panel branding (title, sidebar, login form)
- Update email templates (subjects, bodies, signatures)
- Update PDF report generation branding
- Update Docker container names and network
- Update config defaults (database name, email sender, APNS topic)
- Update README and documentation

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

.env.example

@@ -6,7 +6,7 @@ TIMEZONE=UTC
 SECRET_KEY=your-secret-key-here-change-this-in-production
 
 # Database Settings (PostgreSQL)
-POSTGRES_DB=mycrib
+POSTGRES_DB=casera
 POSTGRES_USER=postgres
 POSTGRES_PASSWORD=change-this-secure-password
 DB_HOST=localhost
@@ -26,13 +26,13 @@ EMAIL_PORT=587
 EMAIL_USE_TLS=true
 EMAIL_HOST_USER=your-email@gmail.com
 EMAIL_HOST_PASSWORD=your-app-password
-DEFAULT_FROM_EMAIL=MyCrib <noreply@mycrib.com>
+DEFAULT_FROM_EMAIL=Casera <noreply@casera.com>
 
 # APNs Settings (iOS Push Notifications)
 APNS_AUTH_KEY_PATH=/path/to/AuthKey_XXXXXX.p8
 APNS_AUTH_KEY_ID=XXXXXXXXXX
 APNS_TEAM_ID=XXXXXXXXXX
-APNS_TOPIC=com.example.mycrib
+APNS_TOPIC=com.example.casera
 APNS_USE_SANDBOX=true
 
 # FCM Settings (Android Push Notifications)