Refactoring of the interaction system and preliminary integration of save/load functionality across the game. (#44)

### Interactables Architecture Refactor
- Converted composition to inheritance, moved from component-based to class-based interactables. No more requirement for chain of "Interactable -> Item" etc.
- Created `InteractableBase` abstract base class with common functionality that replaces the old component
- Specialized child classes: `Pickup`, `ItemSlot`, `LevelSwitch`, `MinigameSwitch`, `CombinationItem`, `OneClickInteraction` are now children classes
- Light updates to the interactable inspector, moved some things arround, added collapsible inspector sections in the  UI for better editor experience

### State Machine Integration
- Custom `AppleMachine` inheritong from Pixelplacement's StateMachine which implements our own interface for saving, easy place for future improvements
- Replaced all previous StateMachines by `AppleMachine`
- Custom `AppleState`  extends from default `State`. Added serialization, split state logic into "EnterState", "RestoreState", "ExitState" allowing for separate logic when triggering in-game vs loading game
- Restores directly to target state without triggering transitional logic
- Migration tool converts existing instances

### Prefab Organization
- Saved changes from scenes into prefabs
- Cleaned up duplicated components, confusing prefabs hierarchies
- Created prefab variants where possible
- Consolidated Environment prefabs and moved them out of Placeholders subfolder into main Environment folder
- Organized item prefabs from PrefabsPLACEHOLDER into proper Items folder
- Updated prefab references - All scene references updated to new locations
- Removed placeholder files from Characters, Levels, UI, and Minigames folders

### Scene Updates
- Quarry scene with major updates
- Saved multiple working versions (Quarry, Quarry_Fixed, Quarry_OLD)
- Added proper lighting data
- Updated all interactable components to new architecture

### Minor editor tools
- New tool for testing cards from an editor window (no in-scene object required)
- Updated Interactable Inspector
- New debug option to opt in-and-out of the save/load system
- Tooling for easier migration

Co-authored-by: Michal Pikulski <michal.a.pikulski@gmail.com>
Reviewed-on: #44

Assets/Scripts/Core/ItemManager.cs

@@ -3,6 +3,7 @@ using System.Collections.Generic;
 using UnityEngine;
 using Interactions;
 using Bootstrap;
+using Core.SaveLoad;
 
 namespace Core
 {
@@ -59,6 +60,7 @@ namespace Core
         {
             // Subscribe to scene load completed so we can clear registrations when scenes change
             SceneManagerService.Instance.SceneLoadStarted += OnSceneLoadStarted;
+            
             Logging.Debug("[ItemManager] Subscribed to SceneManagerService events");
         }
 
@@ -244,5 +246,36 @@ namespace Core
 
         public IEnumerable<Pickup> Pickups => _pickups;
         public IEnumerable<ItemSlot> ItemSlots => _itemSlots;
+
+        /// <summary>
+        /// Gets all registered pickups. Used by save/load system to find items by save ID.
+        /// </summary>
+        public IEnumerable<Pickup> GetAllPickups() => _pickups;
+
+        /// <summary>
+        /// Gets all registered item slots. Used by save/load system.
+        /// </summary>
+        public IEnumerable<ItemSlot> GetAllItemSlots() => _itemSlots;
+
+        /// <summary>
+        /// Finds a pickup by its save ID. Used by save/load system to restore item references.
+        /// </summary>
+        /// <param name="saveId">The save ID to search for</param>
+        /// <returns>The pickup's GameObject if found, null otherwise</returns>
+        public GameObject FindPickupBySaveId(string saveId)
+        {
+            if (string.IsNullOrEmpty(saveId)) return null;
+
+            // Search through all registered pickups
+            foreach (var pickup in _pickups)
+            {
+                if (pickup is SaveableInteractable saveable && saveable.GetSaveId() == saveId)
+                {
+                    return pickup.gameObject;
+                }
+            }
+
+            return null;
+        }
     }
 }