fix(api): correct source_type column to TEXT in sources schema

The database seeding was failing with a JSON syntax error because the `sources` table defined the `source_type` column as `JSONB`, but the `Source` model provides this value as a simple string (from an enum).

This change corrects the `source_type` column type to `TEXT`, aligning the database schema with the data model and resolving the final seeding error.

Author: fulleni

lib/src/services/database_seeding_service.dart

@@ -79,7 +79,7 @@ class DatabaseSeedingService {
             language TEXT,
             status TEXT,
             type TEXT,
-            source_type JSONB,
+            source_type TEXT,
             headquarters_country_id TEXT REFERENCES countries(id),
             created_at TIMESTAMPTZ NOT NULL DEFAULT NOW(),
             updated_at TIMESTAMPTZ