feat: implementar 12 mejoras, tests, docs y optimizaciones

- Fase A: license templates, search history, cost estimator
- Fase B: import URL, bulk ZIP, batch download
- Fase C: comparison mode, mesh validation, measurement tool
- Fase D: cross-section clipping, overhang heatmap, layer animation
- Refactor Pydantic/SQLAlchemy warnings
- 24 tests pytest
- README actualizado
- WebP thumbnails, lazy loading, cache headers

app/migrate.py

@@ -0,0 +1,59 @@
+import os
+from sqlalchemy import text
+from app.database import engine, SessionLocal
+from app.models import Base, Tag, ModelFile
+
+
+def run_migrations():
+    """Run manual migrations for SQLite."""
+    Base.metadata.create_all(bind=engine)
+
+    db = SessionLocal()
+    try:
+        # Check if we need to migrate old tags (CSV string) to new tag structure
+        result = db.execute(text("SELECT name FROM sqlite_master WHERE type='table' AND name='tags'"))
+        if result.fetchone():
+            # Check if there are models with old-style tags (comma separated) and no model_tags entries
+            from app.models import Model3D
+            models = db.query(Model3D).all()
+            for model in models:
+                # Migrate tags if model has tags string but no tag relationships
+                if not model.tags and model.__dict__.get('tags_col'):
+                    tag_names = [t.strip().lower() for t in model.tags_col.split(',') if t.strip()]
+                    for name in tag_names:
+                        tag = db.query(Tag).filter(Tag.name == name).first()
+                        if not tag:
+                            tag = Tag(name=name)
+                            db.add(tag)
+                            db.flush()
+                        if tag not in model.tags:
+                            model.tags.append(tag)
+
+        # Check if we need to migrate files to model_files
+        result = db.execute(text("SELECT name FROM sqlite_master WHERE type='table' AND name='model_files'"))
+        if result.fetchone():
+            from app.models import Model3D
+            models = db.query(Model3D).all()
+            for model in models:
+                # Check if model already has file records
+                if not model.files:
+                    file_path = os.path.join("uploads", model.filename)
+                    if os.path.exists(file_path):
+                        mf = ModelFile(
+                            model_id=model.id,
+                            filename=model.filename,
+                            file_path=file_path,
+                            file_type='stl',
+                            is_primary=True,
+                            file_size=model.file_size,
+                            file_hash=model.file_hash,
+                        )
+                        db.add(mf)
+
+        db.commit()
+        print("Migrations completed successfully")
+    except Exception as e:
+        print(f"Migration error: {e}")
+        db.rollback()
+    finally:
+        db.close()