feat: Enhance interaction and inventory systems with new components and functionality

- Added BPC_UsableWorldObjectSystem for handling various interactable world objects with detailed manual implementation guide.
- Introduced BPC_ActiveItemSystem to manage quick slots and active item usage, including cycling and selection logic.
- Implemented BPC_DocumentArchiveSystem for managing collectible documents with read tracking and categorization.
- Developed BPC_JournalSystem for narrative entries with auto-adding features based on gameplay events.
- Created BPC_KeyItemSystem for key management with consumable and persistent key support.
- Enhanced BPC_FirearmSystem for ranged weapon mechanics, including hitscan and projectile firing.
- Updated BPC_MeleeSystem for melee combat with combo and blocking mechanics.
- Established BPC_ReloadSystem for managing weapon reloading processes, including partial reloads and state management.

docs/blueprints/08-weapons/74_BPC_FirearmSystem.md

@@ -102,4 +102,61 @@ Ranged weapon specialization. Handles line trace / projectile fire, weapon sprea
 - Spread is cumulative while firing, resets on recovery timer.
 - Projectile type requires a child BP implementing `AP_BaseProjectile` with velocity and lifetime.
 - Renamed from `BP_RangedWeapon` to `BPC_FirearmSystem` per Master naming convention.
-- Cross-references updated: `BPC_DamageHandlerComponent` → `BPC_DamageReceptionSystem`, `BPC_PlayerCameraManager` → `BPC_CameraStateLayer`, `DA_WeaponData` → `14-data-assets/`.
+- Cross-references updated: `BPC_DamageHandlerComponent` → `BPC_DamageReceptionSystem`, `BPC_PlayerCameraManager` → `BPC_CameraStateLayer`, `DA_WeaponData` → `14-data-assets/`.
+
+---
+
+## Manual Implementation Guide
+
+### Class Setup
+1. Create Blueprint Class: Parent = `ActorComponent`, Name = `BPC_FirearmSystem`
+2. Attach to `BP_WeaponBase` subclass: `BP_RangedWeapon`
+3. Add FireSocket SceneComponent on weapon mesh (muzzle position)
+
+### Variable Init (BeginPlay)
+```
+Event BeginPlay
+  ├─ Read WeaponData from Owner BP_WeaponBase
+  ├─ Set FireType = WeaponData.FireType (Hitscan/Projectile/Hybrid)
+  ├─ Set Range = WeaponData.EffectiveRange
+  ├─ Set SpreadAngle = WeaponData.BaseSpread
+  ├─ Set BulletsPerShot = WeaponData.PelletsPerShot
+  ├─ Set CurrentSpread = 0.0
+  └─ Cache: BPC_AmmoComponent, BPC_CombatFeedbackComponent, BPC_CameraStateLayer
+```
+
+### Function Node-by-Node
+
+#### `OnFire_Implementation()` *(Overrides BP_WeaponBase.OnFire)*
+```
+Step 1: Get Camera Forward Vector
+Step 2: Switch on FireType:
+  Hitscan: ForLoop (BulletsPerShot):
+    AimDir = Forward + CalculateSpread()
+    LineTraceByChannel: Start=Camera, End=Camera+AimDir*Range
+    If Hit & Implements I_Damageable: ApplyDamage(WeaponData.Damage, HitResult)
+    SpawnImpactFX(HitResult)
+  Projectile: ForLoop (BulletsPerShot):
+    Spawn ProjectileClass at FireSocket, velocity=AimDir*Speed
+  Hybrid: Hitscan + projectile for near-miss area
+Step 3: ApplyRecoil → CameraShake or AddControllerPitch/Yaw
+Step 4: ConsumeAmmo on BPC_AmmoComponent
+Step 5: PlayMuzzleFlash + PlayFireSound on CombatFeedback
+Step 6: CurrentSpread += SpreadIncreasePerShot (clamped to MaxSpread)
+```
+
+#### `CalculateSpread()` → Vector *(Pure)*
+```
+RandomFloat(-1,1)*CurrentSpread → YawOffset
+RandomFloat(-1,1)*CurrentSpread → PitchOffset
+MakeRotator(PitchOffset, YawOffset, 0) → GetForwardVector
+```
+
+### Build Checklist
+- [ ] Create BPC_FirearmSystem, attach to BP_RangedWeapon
+- [ ] Add FireSocket at muzzle
+- [ ] Implement OnFire with hitscan/projectile/hybrid switch
+- [ ] Implement CalculateSpread
+- [ ] Wire to AmmoComponent, CombatFeedback, CameraStateLayer
+- [ ] Create ProjectileClass with ProjectileMovement for projectile weapons
+- [ ] Test: fire at target → damage registers → FX plays → ammo count drops