feat(gameplay): implement in-system onboarding with docked station view

Implement the final onboarding step where the player loads into their
selected starting system docked at a station.

New features:
- Create in_system module for system-scale gameplay
- Spawn player ship docked at highest-population station
- Display station info panel with undock button
- Position camera for cinematic docked view with orbit controls

Implementation details:
- in_system/mod.rs: Plugin setup with DockedState and ActiveSystem resources
- in_system/scene.rs: System/POI spawning and player ship docked positioning
- in_system/docked.rs: Docked state management and UndockEvent
- in_system/ui.rs: Docked UI with station details and undock button
- Reuse existing POI spawning patterns from galaxy/contents.rs
- Select docking station by highest population (better for new players)

Modified files:
- Add in_system module exports to gameplay/mod.rs
- Register InSystemPlugin in main.rs
- Update orbit camera control for InGame state
- Re-export GeneratedStation and STARTING_SHIPS for use by in_system

The player now completes onboarding by loading into a system view with
their ship docked at a station, ready for gameplay.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

apps/game/src/gameplay/character_creation/mod.rs

@@ -16,7 +16,7 @@ mod ui;
 // exported so consumers can `use crate::gameplay::character_creation::Origin`
 // without us remembering to re-add the re-export the day they're needed.
 #[allow(unused_imports)]
-pub use params::{CharacterDraft, Origin, StartingShip};
+pub use params::{CharacterDraft, Origin, StartingShip, STARTING_SHIPS};
 
 use bevy::prelude::*;