fix: merge main branch and renumber migration 037→040

Resolve all merge conflicts between our automation feature branch and
current main (v0.163.0, 920 commits ahead).

Conflicts resolved:
- app/api/__init__.py: add automation_router alongside main's new routers
  (classification_rules, qr_auth, sessions, system_reset)
- app/config.py: add main's new settings (dropbox_use_global_credentials,
  factory_reset_on_startup, enable_factory_reset)
- app/models.py: add main's new models (ClassificationRuleModel, UserSession,
  QRLoginChallenge, SharePoint integration type)
- app/utils/settings_service.py: merge automation_hooks_enabled with main's
  new metadata entries
- docs/API.md: merge automation API docs with main's classification rules docs
- docs/ConfigurationGuide.md: add factory reset settings
- tests/conftest.py: import both AutomationHook and new main models

Migration renumbered:
- 037_add_automation_hooks → 040_add_automation_hooks
- down_revision: 039_add_classification_rules (was 036_add_document_translation_fields)
- Chain: 036 → 037 → 038 → 039 → 040 (automation hooks)

For all non-automation files with conflicts, main's version was taken since
our branch did not modify those files (conflicts were from a stale prior merge).

Co-authored-by: christianlouis <361235+christianlouis@users.noreply.github.com>
Agent-Logs-Url: https://github.com/christianlouis/DocuElevate/sessions/cb62f012-3b69-4415-835e-3857ce3e9f45

app/database.py

@@ -10,6 +10,7 @@ from typing import Any
 from sqlalchemy import create_engine, exc
 from sqlalchemy.engine.url import make_url
 from sqlalchemy.orm import Session, declarative_base, sessionmaker
+from sqlalchemy.pool import NullPool, QueuePool
 
 from app.config import settings
 
@@ -17,9 +18,37 @@ logger = logging.getLogger(__name__)
 
 Base = declarative_base()
 
-# Parse the DATABASE_URL
+# ---------------------------------------------------------------------------
+# Engine construction
+# ---------------------------------------------------------------------------
 DB_URL = settings.database_url
-engine = create_engine(DB_URL, connect_args={"check_same_thread": False})
+_parsed_url = make_url(DB_URL)
+
+_connect_args: dict[str, Any] = {}
+_engine_kwargs: dict[str, Any] = {
+    "pool_pre_ping": True,  # detect stale / dropped connections before use
+}
+
+if _parsed_url.get_backend_name() == "sqlite":
+    # SQLite does not benefit from connection pooling and is prone to
+    # QueuePool exhaustion under concurrent access.  NullPool opens a fresh
+    # connection for each request and closes it immediately afterwards,
+    # completely avoiding the "QueuePool limit reached" TimeoutError.
+    _connect_args["check_same_thread"] = False
+    _engine_kwargs["poolclass"] = NullPool
+else:
+    # PostgreSQL / MySQL — use a bounded QueuePool with configurable limits.
+    _engine_kwargs["poolclass"] = QueuePool
+    _engine_kwargs.update(
+        {
+            "pool_size": settings.db_pool_size,
+            "max_overflow": settings.db_max_overflow,
+            "pool_timeout": settings.db_pool_timeout,
+            "pool_recycle": settings.db_pool_recycle,
+        }
+    )
+
+engine = create_engine(DB_URL, connect_args=_connect_args, **_engine_kwargs)
 SessionLocal = sessionmaker(autocommit=False, autoflush=False, bind=engine)