1.1.5: fix activation analytics blind spots + purchase environment tagging

- dish_added now carries a `source` param; onboarding-created dishes fire
  it with source="onboarding" (previously untracked, undercounting activation)
- onboarding_completed now reports dish_count
- premium_purchased tagged with StoreKit environment (production/sandbox/xcode)
  so test purchases can be excluded from conversion metrics
- add .gitignore to keep signing secrets (.p12/.cer/.mobileprovision) and
  build artifacts out of the repo
- document branch↔MARKETING_VERSION naming convention

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01UtWT52pAE91D7mbDda1cAM

.gitignore

@@ -0,0 +1,22 @@
+# Signing secrets — NEVER commit
+*.p12
+*.p8
+*.cer
+*.certSigningRequest
+*.mobileprovision
+
+# Build artifacts
+*.ipa
+*.dSYM.zip
+/build/
+DerivedData/
+
+# Fastlane generated
+fastlane/report.xml
+fastlane/Preview.html
+fastlane/test_output/
+
+# macOS / Xcode
+.DS_Store
+*.xcuserstate
+xcuserdata/