feat(mobile): switch iOS code signing to fastlane match

- Replace manual certificate and provisioning profile handling with fastlane match
- Match automatically syncs certificates and profiles from a private git repository
- Simplifies CI/CD workflow by removing 8 secrets (replaced with 2: MATCH_PASSWORD and MATCH_GIT_BASIC_AUTHORIZATION)
- Add new lanes: sync_certificates and regenerate_certificates for easier maintenance
- When certificates expire, just run 'fastlane regenerate_certificates' locally

Benefits:
- Single source of truth for code signing
- Automatic certificate/profile management
- Easier onboarding for new team members
- Simpler secret rotation when certificates expire

Required new GitHub secrets:
- MATCH_PASSWORD: Encryption password for the match repository
- MATCH_GIT_BASIC_AUTHORIZATION: base64(username:token) for repo access

Removed secrets (no longer needed):
- IOS_CERTIFICATE_P12
- IOS_CERTIFICATE_PASSWORD
- IOS_PROVISIONING_PROFILE
- IOS_PROVISIONING_PROFILE_SHARE_EXTENSION
- IOS_PROVISIONING_PROFILE_WIDGET_EXTENSION
- IOS_DEVELOPMENT_PROVISIONING_PROFILE
- IOS_DEVELOPMENT_PROVISIONING_PROFILE_SHARE_EXTENSION
- IOS_DEVELOPMENT_PROVISIONING_PROFILE_WIDGET_EXTENSION

mobile/ios/fastlane/Matchfile

@@ -0,0 +1,19 @@
+git_url(ENV["MATCH_GIT_URL"] || "https://github.com/immich-app/ios-certs")
+
+storage_mode("git")
+
+type("appstore")
+
+team_id("2F67MQ8R79")
+
+app_identifier([
+  "app.alextran.immich",
+  "app.alextran.immich.ShareExtension",
+  "app.alextran.immich.Widget",
+  "app.alextran.immich.development",
+  "app.alextran.immich.development.ShareExtension",
+  "app.alextran.immich.development.Widget"
+])
+
+# For all available options run `fastlane match --help`
+# The docs are available on https://docs.fastlane.tools/actions/match