feat(stats): wire history and round detail to the real round ledger

[netqo]

Summary

Phase 1 of the stats layer: connects the persisted game_round ledger (added with Coinflip) into the two screens that were still rendering preview data. History (CU-10) now lists the rounds actually played with a live aggregate summary, and Round Detail (CU-11) resolves a round by id and shows its real, verifiable provably-fair seeds.

Rationale

The round ledger existed but had no readers. Wiring History + Round Detail first delivers the marquee defense feature (real provably-fair verification) and is self-contained:

• HistoryViewModel maps GameRepository.rounds into the existing HistoryData (rows + summary: rounds, win rate, net). Search/filter stay screen-local. A "no rounds yet" empty state is distinguished from the filtered-out "no rounds match".
• RoundDetailViewModel reads the nav-arg id, resolves the round via the new GameRepository.getRound, and exposes Loading / Success / NotFound; RoundDetailScreen is now stateless over that state (matching the Wallet/News pattern). The provably-fair block carries the round's real serverSeed / clientSeed / nonce / HMAC hash.
• The round -> RoundDetailData mapping is coinflip-shaped for now (no crash bar) and branches on GameRound.game, so the other games slot in as they land.

Profile P&L is intentionally left on preview data; it is the next slice (kept out to keep this PR scoped and avoid destabilizing the Profile tests).

Also fixes CoinflipScreenTest, which still called the pre-stateless CoinflipScreen signature from the Coinflip PR. The "assemble and unit tests" CI job does not compile the instrumented sources, so it was not caught; this PR compiles them locally.

Verification

• ./gradlew testDebugUnitTest detekt ktlintCheck assembleDebug compileDebugAndroidTestKotlin green locally (JDK 17).
• New tests: HistoryViewModelTest, RoundDetailViewModelTest, getRound cases in GameRepositoryImplTest.
• Installed the debug APK on a physical device: played coinflip rounds, saw them list in History with a correct summary, opened a round and expanded Provably Fair to confirm the real seeds/nonce/hash render.

Test plan

• History lists played rounds newest-first with Bet/Payout/Prediction.
• The summary strip (rounds, win rate, net) reflects the real rounds.
• Game/Result filters and search work over the rounds.
• An empty ledger shows "No rounds yet".
• Tapping a round opens Round Detail with the real outcome.
• Provably Fair expands to the round's real seeds / nonce / hash.
• Back returns to History.

Related issues

Refs the stats-layer work for the final entrega (phase 1 of 2; profile P&L is phase 2).

Checklist

• Commit messages follow Conventional Commits (see CONTRIBUTING.md).
• Branch name follows the naming convention (feat/, fix/, chore/, etc.).
• The change is scoped: no unrelated edits sneaked into this PR.
• If user-visible behavior changed, CHANGELOG.md has been updated under [Unreleased].
• If a new dependency was added, it is justified in the PR description. (No new dependencies.)