feat(phase-1): Complete foundation setup

- Add User model and authentication system with JWT cookies
- Implement login/logout routes and protected dashboard
- Add Alembic database migration configuration
- Add create_admin.py script for initial user setup
- Make ContentGenerator and ImageGenerator lazy-initialized
- Add comprehensive API keys setup documentation
- Fix startup errors when services unavailable

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

app/services/content_generator.py

@@ -13,12 +13,21 @@ class ContentGenerator:
     """Generador de contenido usando DeepSeek API."""
 
     def __init__(self):
-        self.client = OpenAI(
-            api_key=settings.DEEPSEEK_API_KEY,
-            base_url=settings.DEEPSEEK_BASE_URL
-        )
+        self._client = None
         self.model = "deepseek-chat"
 
+    @property
+    def client(self):
+        """Lazy initialization del cliente OpenAI."""
+        if self._client is None:
+            if not settings.DEEPSEEK_API_KEY:
+                raise ValueError("DEEPSEEK_API_KEY no configurada. Configura la variable de entorno.")
+            self._client = OpenAI(
+                api_key=settings.DEEPSEEK_API_KEY,
+                base_url=settings.DEEPSEEK_BASE_URL
+            )
+        return self._client
+
     def _get_system_prompt(self) -> str:
         """Obtener el prompt del sistema con la personalidad de la marca."""
         return f"""Eres el Community Manager de {settings.BUSINESS_NAME}, una empresa de tecnología ubicada en {settings.BUSINESS_LOCATION}.