feat(world): add persistent citizen simulation with needs, jobs, and social features

- Adds Character model with survival needs (hunger, thirst, energy) and state machine
- Implements city:tick world ticker for offline progression every minute
- Adds city territory expansion and building construction system
- Introduces job economy, inventory, and transaction audit trail
- Adds social graph (friends, marriage, children) and character chat
- Implements admin approval workflow for new registrations
- Adds hospital admission system for traffic accidents
- Includes comprehensive feature tests and world seeders

app/Models/Building.php

@@ -0,0 +1,68 @@
+<?php
+
+namespace App\Models;
+
+use Illuminate\Database\Eloquent\Attributes\Fillable;
+use Illuminate\Database\Eloquent\Model;
+use Illuminate\Database\Eloquent\Relations\BelongsTo;
+
+/**
+ * Player-constructed structure placed on free terrain inside a city.
+ *
+ * Construction advances through build_progress on each world tick until the
+ * building is complete; finished houses become the owner's residence.
+ */
+#[Fillable([
+    'city_id', 'owner_character_id', 'type', 'name',
+    'pos_x', 'pos_z', 'width', 'depth', 'height',
+    'is_complete', 'build_progress',
+])]
+class Building extends Model
+{
+    public const TYPE_HOUSE = 'house';
+
+    /**
+     * Public hospital where accident victims are admitted.
+     *
+     * @var string
+     */
+    public const TYPE_HOSPITAL = 'hospital';
+
+    /**
+     * City containing this building.
+     *
+     * @return BelongsTo<City, $this>
+     */
+    public function city(): BelongsTo
+    {
+        return $this->belongsTo(City::class);
+    }
+
+    /**
+     * Character that commissioned the building.
+     *
+     * @return BelongsTo<Character, $this>
+     */
+    public function owner(): BelongsTo
+    {
+        return $this->belongsTo(Character::class, 'owner_character_id');
+    }
+
+    /**
+     * Get the attributes that should be cast.
+     *
+     * @return array<string, string>
+     */
+    protected function casts(): array
+    {
+        return [
+            'pos_x' => 'float',
+            'pos_z' => 'float',
+            'width' => 'float',
+            'depth' => 'float',
+            'height' => 'float',
+            'is_complete' => 'boolean',
+            'build_progress' => 'integer',
+        ];
+    }
+}