feat(game): introduce GameMode enum and mode-aware session/orchestrator

[TheMeinerLP]

Description

The GameOrchestrator and GameSession currently have no concept of a game mode. Both Race Mode and Practice Mode require branching behavior across phases, scoring, HUD, and persistence. This epic introduces a `GameMode` enum (`RACE`, `PRACTICE`), threads it through `GameSession`, `GameOrchestrator`, `GamePhaseFactory`, and `GameResultPersistenceService`, and adds a `gameMode` column to `game_results` via DB migration. No user-visible behavior changes — purely structural scaffolding.

Blocks all other game mode epics.

Acceptance Criteria

• `GameMode` enum with `RACE` and `PRACTICE` values exists in `shared/common`
• `GameSession` carries a `GameMode` field (non-null, set at session creation)
• `GameOrchestrator` selects phase chains and scoring strategy based on `GameMode`
• `GamePhaseFactory` creates mode-appropriate phases
• `GameResultPersistenceService` records `gameMode` on every result
• DB migration adds `gameMode` column to `game_results` table (non-null, default `RACE`)
• No user-visible behavior change — all existing behavior maps to `RACE`
• ArchUnit tests pass (no cross-module boundary violations)
• Unit tests cover `GameMode` routing in orchestrator and phase factory

Technical Details

• `GameMode` belongs in `shared/common` (or `shared/api`) — zero platform imports
• Follow the Enum DSL pattern (cached `VALUES`, `byName()`/`byId()` lookup, `@Nullable` return)
• `GameSession` uses the Interface+Impl pattern; add `gameMode()` to the interface
• DB migration must be Hibernate-compatible (add column, not recreate table)
• `GamePhaseFactory` should use a sealed interface hierarchy per ManisGame pattern

Dependencies

None — this is the prerequisite epic for all other game mode work.

Estimate

L

[voyager-release-bot]

🎉 This issue has been resolved in version 1.7.0 🎉

The release is available on GitHub release

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