feat: remove send tab, default tips on, drop tipping beta flag

[bmc08gt]

Summary

Removes the Send tab (nav button), launches tipping as an always-on feature (dropping the Tipping beta flag), and stops handling chat deeplinks.

Send tab

• Delete NavBarButton.Send, the NavigationBar button + preview, ScannerDecorItem.Send + the scanner mapping.
• Disconnect the direct-send flow from the build: remove AppRoute.Sheets.Send, the nav-graph entry, the settings.gradle.kts include, and the app module dep.
• The direct-send feature module (and core/send/SendStep.kt) are kept on disk but no longer built — parked so the flow can be re-enabled later by re-wiring it (re-add to settings.gradle.kts + app dep, restore AppRoute.Sheets.Send + the nav entry + the nav-bar button).
• Rework NavBarConfigTest for the new default order [Discover, Give, Tips, Wallet] and add a regression test that a persisted order containing the removed "Send" token deserializes cleanly (dropped + back-filled) rather than crashing on upgrade.

Tipping (launched)

• Delete FeatureFlag.Tipping (definition + title/message) — tips are on for all users. Remove the session observer + isTippingEnabled state, and strip the now-orphaned FeatureFlagController dependency from TippingCoordinator. The Tips tab is always shown.

Chat deeplinks

• Remove DeeplinkType.Chat and isChat/handleChat from AppRouter. /chat/{id} links now fall through unhandled and land on the camera (documented in classify() so the routing isn't re-added by accident). Tip DMs still route via /tip/chat/.
• Fold non-tip and contact-addressed chat push notifications into a plain launch intent; delete the now-dead Linkify.chatById/chatByPhone.
• The app.flipcash.com/chat/.* manifest intent filter is intentionally kept so links still open the app (→ camera); send.flipcash.com cash links are untouched.

Maestro

• Delete direct_send.yaml and send_to_contact.yaml (they tapped the removed tab), drop the dead tipping_enabled beta-flag args (tipping is default-on), and update the README.

Testing

• ./gradlew :apps:flipcash:app:assembleDebug → BUILD SUCCESSFUL (parked direct-send module is not in the build and is ignored).
• Unit tests pass for every touched module: core, shared:session, shared:tipping, shared:router, shared:featureflags, shared:notifications, features:scanner, app.

29 files changed, +57 / −245.