🗃️ Add database schema, models & seeders (Story 1.2)

Migrations (translations, projects, skills, skill_project), Eloquent models
with belongsToMany relations, scopes, and test seeders (74 translations FR/EN,
10 skills, 3 projects, 12 skill-project links).

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

api/database/migrations/2026_02_05_000001_create_translations_table.php

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+<?php
+
+use Illuminate\Database\Migrations\Migration;
+use Illuminate\Database\Schema\Blueprint;
+use Illuminate\Support\Facades\Schema;
+
+return new class extends Migration
+{
+    public function up(): void
+    {
+        Schema::create('translations', function (Blueprint $table) {
+            $table->id();
+            $table->string('lang', 5);
+            $table->string('key_name', 255);
+            $table->text('value');
+            $table->timestamps();
+
+            $table->unique(['lang', 'key_name'], 'unique_translation');
+            $table->index('lang', 'idx_lang');
+        });
+    }
+
+    public function down(): void
+    {
+        Schema::dropIfExists('translations');
+    }
+};

api/database/migrations/2026_02_05_000002_create_projects_table.php

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+<?php
+
+use Illuminate\Database\Migrations\Migration;
+use Illuminate\Database\Schema\Blueprint;
+use Illuminate\Support\Facades\Schema;
+
+return new class extends Migration
+{
+    public function up(): void
+    {
+        Schema::create('projects', function (Blueprint $table) {
+            $table->id();
+            $table->string('slug')->unique();
+            $table->string('title_key');
+            $table->string('description_key');
+            $table->string('short_description_key');
+            $table->string('image')->nullable();
+            $table->string('url')->nullable();
+            $table->string('github_url')->nullable();
+            $table->date('date_completed');
+            $table->boolean('is_featured')->default(false);
+            $table->integer('display_order')->default(0);
+            $table->timestamps();
+
+            $table->index('display_order');
+        });
+    }
+
+    public function down(): void
+    {
+        Schema::dropIfExists('projects');
+    }
+};

api/database/migrations/2026_02_05_000003_create_skills_table.php

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+<?php
+
+use Illuminate\Database\Migrations\Migration;
+use Illuminate\Database\Schema\Blueprint;
+use Illuminate\Support\Facades\Schema;
+
+return new class extends Migration
+{
+    public function up(): void
+    {
+        Schema::create('skills', function (Blueprint $table) {
+            $table->id();
+            $table->string('slug')->unique();
+            $table->string('name_key');
+            $table->string('description_key');
+            $table->string('icon')->nullable();
+            $table->string('category');
+            $table->integer('max_level')->default(5);
+            $table->integer('display_order')->default(0);
+            $table->timestamps();
+
+            $table->index('category');
+        });
+    }
+
+    public function down(): void
+    {
+        Schema::dropIfExists('skills');
+    }
+};

api/database/migrations/2026_02_05_000004_create_skill_project_table.php

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+<?php
+
+use Illuminate\Database\Migrations\Migration;
+use Illuminate\Database\Schema\Blueprint;
+use Illuminate\Support\Facades\Schema;
+
+return new class extends Migration
+{
+    public function up(): void
+    {
+        Schema::create('skill_project', function (Blueprint $table) {
+            $table->id();
+            $table->foreignId('skill_id')->constrained()->cascadeOnDelete();
+            $table->foreignId('project_id')->constrained()->cascadeOnDelete();
+            $table->integer('level_before');
+            $table->integer('level_after');
+            $table->string('level_description_key')->nullable();
+            $table->timestamps();
+
+            $table->unique(['skill_id', 'project_id']);
+        });
+    }
+
+    public function down(): void
+    {
+        Schema::dropIfExists('skill_project');
+    }
+};