feat: Implement SQLite support with environment-driven backend switching

changelog.md

@@ -15,6 +15,7 @@
 - Resolved Ruff E402 warnings by moving module docstrings ahead of `from __future__ import annotations` across currency and pricing service modules, dropped the unused `HTTPException` import in `monitoring/__init__.py`, and confirmed a clean `ruff check .` run.
 - Enhanced the deploy job in `.gitea/workflows/cicache.yml` to capture Kubernetes pod, deployment, and container logs into `/logs/deployment/` for staging/production rollouts and publish them via a `deployment-logs` artifact, updating CI/CD documentation with retrieval instructions.
 - Fixed CI dashboard template lookup failures by renaming `templates/Dashboard.html` to `templates/dashboard.html` and verifying `tests/test_dashboard_route.py` locally to ensure TemplateNotFound no longer occurs on case-sensitive filesystems.
+- Implemented SQLite support as primary local database with environment-driven backend switching (`CALMINER_USE_SQLITE=true`), updated `scripts/init_db.py` for database-agnostic DDL generation (PostgreSQL enums vs SQLite CHECK constraints), tested compatibility with both backends, and verified application startup and seeded data initialization work seamlessly across SQLite and PostgreSQL.
 
 ## 2025-11-11
 

config/database.py

@@ -11,12 +11,21 @@ def _build_database_url() -> str:
     """Construct the SQLAlchemy database URL from granular environment vars.
 
     Falls back to `DATABASE_URL` for backward compatibility.
+    Supports SQLite when CALMINER_USE_SQLITE is set.
     """
 
     legacy_url = os.environ.get("DATABASE_URL", "")
     if legacy_url and legacy_url.strip() != "":
         return legacy_url
 
+    use_sqlite = os.environ.get("CALMINER_USE_SQLITE", "").lower() in ("true", "1", "yes")
+    if use_sqlite:
+        # Use SQLite database
+        db_path = os.environ.get("DATABASE_PATH", "./data/calminer.db")
+        # Ensure the directory exists
+        os.makedirs(os.path.dirname(db_path), exist_ok=True)
+        return f"sqlite:///{db_path}"
+
     driver = os.environ.get("DATABASE_DRIVER", "postgresql")
     host = os.environ.get("DATABASE_HOST")
     port = os.environ.get("DATABASE_PORT", "5432")