chore(analytics): add tipping flow tracking (scan funnel + sent tip)

[bmc08gt]

What

Adds analytics to the tipping flows, mirroring the existing send/chat analytics (Sent Cash / Sent Message). Covers both the scanned tip-card flow and the chat side.

New events

Event	Fires when	Properties
Tip Card Scanned	An OpenCode tip payload is scanned (CodeScanDelegate.onTipCardScanned)	—
Tip Card Presented	A scanned/deeplinked tip card resolves and is presented (TipCardDelegate)	—
Sent Tip	A tip completes — from the scanned-card flow or an in-chat tip DM	Fiat, Currency, State, … (same as Sent Cash)

Existing Sent Message now carries a Chat Type property (Tip / Contact / Unknown).

This gives a funnel: Tip Card Scanned → Tip Card Presented → Sent Tip.

How

• Analytics.Transfer.SentTip → standalone "Sent Tip" event (fired via the existing transfer() plumbing, so it carries amount/state/error). Intentionally not a ChatEvent, since the scanned-card path is not a chat.
• AnalyticsEvent.TipCardEvent.Scanned / .Presented, plus tipCardScanned() / tipCardPresented() on the service interface (wired through MixpanelAnalyticsDelegate and the stub).
• messageSentInChat(type: ChatType, …) — ChatViewModel derives the type from the resolved participant (TipUser → TIP_DM, Contact → CONTACT_DM).
• In-chat payments branch to SentTip vs SentCash on participant type.
• TippingCoordinator.confirmTip() — injected FlipcashAnalyticsService and activated the previously commented-out tracking as SentTip.

Testing

• :analytics, :session, :tipping, :messenger all compile (compileDebugKotlin).
• No behavior change beyond analytics emission.