feat: AppsFlyer unified deep linking to registration screen

[dariakharlan]

Summary

• Integrates the AppsFlyer Android SDK for Unified Deep Linking (UDL), mirroring the existing Branch integration pattern in this codebase.
• Deep links from go.proanalytics.academy, proanalytics.onelink.me, and the academyapp:// custom scheme resolve through a new AppsFlyerDeepLinkHandler and route to the registration (sign-up) screen by default. A OneLink template can override the destination by setting a screen_name deep link parameter, reusing the existing DeepLink/DeepLinkRouter infrastructure.
• New APPSFLYER.ENABLED / APPSFLYER.DEV_KEY config keys (default config.yaml for dev/stage/prod), following the same pattern as BRANCH.
• Manifest intent-filters added for the custom scheme and the two App Links domains (autoVerify="true").
• Added tools:replace for allowBackup/dataExtractionRules/fullBackupContent on <application>, required because the AppsFlyer SDK ships its own manifest entries for these that otherwise fail the manifest merge.

Why

Support AppsFlyer-driven install/re-engagement attribution and route new users straight to registration when they arrive via a tracked link, without disrupting the existing Branch-based deep link flows (course/discussion links, etc.).

Notes for reviewers

• APPSFLYER.ENABLED defaults to false and DEV_KEY is empty in all three environments — the SDK will not initialize until a real dev key is configured.
• For the App Links domains to auto-verify, Digital Asset Links JSON needs to be published on go.proanalytics.academy and proanalytics.onelink.me (handled via AppsFlyer's OneLink setup).
• Full :app compile could not be verified in the dev environment used for this change due to a pre-existing, unrelated MSAL dependency issue in the auth module (reproducible on main without this change). The core module (housing the new config classes) compiles cleanly, and the app-module changes closely follow the already-working Branch pattern.

Test plan

• Set APPSFLYER.ENABLED: true and a real DEV_KEY in the target environment's config.yaml
• Build and install the app
• Trigger a OneLink click (or adb shell am start -a android.intent.action.VIEW -d "academyapp://test") and confirm the app opens to the registration screen
• Verify existing Branch deep links (course/discussion) still work unaffected

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