feat(ai): add per-character AI model assignment and identity profiles

Implements deterministic model resolution (column → env map → pool →
default) and adds AI identity fields to characters. Migration backfills
existing rows with deterministic defaults. Controller uses resolved model
and identity block in system prompts for contextual conversations.

database/migrations/2026_10_31_210846_add_ai_profile_to_characters_table.php

@@ -0,0 +1,67 @@
+<?php
+
+use Illuminate\Database\Migrations\Migration;
+use Illuminate\Database\Schema\Blueprint;
+use Illuminate\Support\Facades\DB;
+use Illuminate\Support\Facades\Schema;
+
+/**
+ * Adds the per-character AI profile to "characters".
+ *
+ * Every citizen can now carry its own model override plus the identity
+ * used by the conversational persona: age, gender, short biography and
+ * personality. Existing rows are backfilled with a deterministic default
+ * persona so no character speaks without one.
+ */
+return new class extends Migration
+{
+    /**
+     * Personality pool used for the backfill (kept inline so this
+     * migration stays a self-contained snapshot).
+     *
+     * @var list<string>
+     */
+    private const PERSONALITIES = [
+        'Extrovertido e curioso, adora puxar conversa com quem passa.',
+        'Tranquilo e observador, fala pouco mas escuta tudo com atenção.',
+        'Bem-humorado e espirituoso, brinca com todo mundo por perto.',
+        'Sério e direto, vai ao ponto sem rodeios.',
+        'Gentil e prestativo, sempre oferece ajuda antes de perguntarem.',
+        'Aventureiro e barulhento, vive contando histórias da cidade.',
+    ];
+
+    /**
+     * Run the migrations.
+     */
+    public function up(): void
+    {
+        Schema::table('characters', function (Blueprint $table): void {
+            $table->string('ai_model', 120)->nullable()->after('name');
+            $table->unsignedSmallInteger('ai_age')->nullable();
+            $table->string('ai_gender', 24)->nullable();
+            $table->string('ai_personality', 255)->nullable();
+            $table->string('ai_bio', 500)->nullable();
+        });
+
+        DB::table('characters')
+            ->whereNull('ai_personality')
+            ->orderBy('id')
+            ->get()
+            ->each(function (object $row): void {
+                DB::table('characters')->where('id', $row->id)->update([
+                    'ai_age' => 18 + (7 * (int) $row->id) % 50,
+                    'ai_personality' => self::PERSONALITIES[(int) $row->id % count(self::PERSONALITIES)],
+                ]);
+            });
+    }
+
+    /**
+     * Reverse the migrations.
+     */
+    public function down(): void
+    {
+        Schema::table('characters', function (Blueprint $table): void {
+            $table->dropColumn(['ai_model', 'ai_age', 'ai_gender', 'ai_personality', 'ai_bio']);
+        });
+    }
+};