feat(shop): add box pickup/carry, pour-into-shelf, and package flight visuals

- Carryable: generic pickup/carry component, cosmetic per-peer follow of
  the carrier's HandSocket instead of NGO reparenting (camera pitch isn't
  networked, so root-level reparenting wouldn't tilt with the view)
- PlayerCarry: mutual exclusion with PlayerHands, server-timed hold-to-pour
  tick (client only signals start/stop, never per-unit requests)
- IPourSource/IPourTarget: decouple PlayerInteractor from concrete Shop
  types, same pattern as IInteractable
- Lieferkarton: gains product data (productId/quantity), two-stage
  Interact() (open, then pick up), IPourSource
- ShelfSlot: implements IPourTarget, fills the previous RefreshVisuals TODO
- PackageDisplay: renders quantity as a proper column x row grid that
  stacks into further layers as space runs out, reused by both containers
- FlyingPackage: small non-networked cosmetic visual that arcs a package
  from the carried box to its exact landing slot in the shelf grid on
  every successful pour tick, broadcast via Rpc(SendTo.Everyone)
- StorageCrate: rejects pickup while the player is carrying a box

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

Assets/Prefabs/Player.prefab

@@ -15,6 +15,7 @@ GameObject:
   - component: {fileID: 6222683508516611630}
   - component: {fileID: 2738588686490111713}
   - component: {fileID: 1819053832086648781}
+  - component: {fileID: 8888888888888888803}
   m_Layer: 0
   m_Name: Player
   m_TagString: Untagged
@@ -215,7 +216,8 @@ Transform:
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   m_LocalScale: {x: 1, y: 1, z: 1}
   m_ConstrainProportionsScale: 0
-  m_Children: []
+  m_Children:
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   m_Father: {fileID: 5481062863680931684}
   m_LocalEulerAnglesHint: {x: 0, y: 0, z: 0}
 --- !u!20 &6771695443112085325
@@ -321,6 +323,53 @@ MonoBehaviour:
     m_VarianceClampScale: 0.9
     m_ContrastAdaptiveSharpening: 0
   m_Version: 2
+--- !u!1 &8888888888888888801
+GameObject:
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+  m_CorrespondingSourceObject: {fileID: 0}
+  m_PrefabInstance: {fileID: 0}
+  m_PrefabAsset: {fileID: 0}
+  serializedVersion: 6
+  m_Component:
+  - component: {fileID: 8888888888888888802}
+  m_Layer: 0
+  m_Name: HandSocket
+  m_TagString: Untagged
+  m_Icon: {fileID: 0}
+  m_NavMeshLayer: 0
+  m_StaticEditorFlags: 0
+  m_IsActive: 1
+--- !u!4 &8888888888888888802
+Transform:
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+  m_PrefabAsset: {fileID: 0}
+  m_GameObject: {fileID: 8888888888888888801}
+  serializedVersion: 2
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+  m_LocalPosition: {x: 0.3, y: -0.2, z: 0.6}
+  m_LocalScale: {x: 1, y: 1, z: 1}
+  m_ConstrainProportionsScale: 0
+  m_Children: []
+  m_Father: {fileID: 7530582357117073923}
+  m_LocalEulerAnglesHint: {x: 0, y: 0, z: 0}
+--- !u!114 &8888888888888888803
+MonoBehaviour:
+  m_ObjectHideFlags: 0
+  m_CorrespondingSourceObject: {fileID: 0}
+  m_PrefabInstance: {fileID: 0}
+  m_PrefabAsset: {fileID: 0}
+  m_GameObject: {fileID: 2721740664708778080}
+  m_Enabled: 1
+  m_EditorHideFlags: 0
+  m_Script: {fileID: 11500000, guid: 6ed618ff659f6684f8c2ce58ba032c35, type: 3}
+  m_Name:
+  m_EditorClassIdentifier: AfterHours.Runtime::AfterHours.Networking.PlayerCarry
+  ShowTopMostFoldoutHeaderGroup: 1
+  _handSocket: {fileID: 8888888888888888802}
+  _pourInterval: 0.4
+  _maxPourReach: 2.5
 --- !u!1 &7157595194792186803
 GameObject:
   m_ObjectHideFlags: 0