feat: seed predefined tags on database initialization

Automatically insert predefined tags when the tags table is empty
during DB init.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/plesna_gerance/database/connection.py

@@ -4,10 +4,10 @@ import os
 from pathlib import Path
 from typing import Generator
 
-from sqlalchemy import create_engine
+from sqlalchemy import create_engine, text
 from sqlalchemy.orm import Session, sessionmaker
 
-from .models import Base
+from .models import Base, Tag
 
 
 # Default database path - relative to project root
@@ -106,9 +106,30 @@ def init_db(db_path: Path | None = None) -> Path:
     _engine = engine
     _SessionLocal = sessionmaker(autocommit=False, autoflush=False, bind=engine)
 
+    # Seed predefined tags if the table is empty
+    _seed_tags_if_empty(engine)
+
     return db_path
 
 
+def _seed_tags_if_empty(engine):
+    """Insert predefined tags if the tags table is empty."""
+    from ..scripts.seed_tags import PREDEFINED_TAGS
+
+    session = Session(bind=engine)
+    try:
+        count = session.execute(text("SELECT COUNT(*) FROM tags")).scalar()
+        if count == 0:
+            for tag_name in PREDEFINED_TAGS:
+                session.add(Tag(nom=tag_name))
+            session.commit()
+    except Exception:
+        session.rollback()
+        raise
+    finally:
+        session.close()
+
+
 def reset_connection():
     """Reset global connection (useful for testing)."""
     global _engine, _SessionLocal