fix(cleanup): resolve 9 low-priority issues (P34-P42)

P34: Remove test_sample plugin from production code
P35: Remove CompanyContact=None dead code from contact.py
P36: Change Plugin.config from Text to JSONB (model + migration 0117 + service)
P37: Add AI comment about workspace overengineering in workspace.py
P38: Add container resource limits to docker-compose.yaml
P39: Guest TTL 1800 not found — already migrated to regular users
P40: Add AI comment about missing IP/Device binding in session.py
P41: Fix Redis healthcheck to use auth password
P42: RLS migration history comment already present in alembic/env.py

app/models/plugin.py

@@ -5,7 +5,8 @@ from __future__ import annotations
 import uuid
 from typing import Any
 
-from sqlalchemy import Boolean, Index, String, Text
+from sqlalchemy import Boolean, Index, String
+from sqlalchemy.dialects.postgresql import JSONB
 from sqlalchemy.dialects.postgresql import UUID as PGUUID
 from sqlalchemy.orm import Mapped, mapped_column
 
@@ -33,8 +34,8 @@ class Plugin(Base, TimestampMixin):
     active: Mapped[bool] = mapped_column(Boolean, nullable=False, default=False)
     is_core: Mapped[bool] = mapped_column(Boolean, nullable=False, default=False)
     config: Mapped[dict[str, Any] | None] = mapped_column(
-        Text,
-        nullable=True,  # JSON string for plugin configuration
+        JSONB,
+        nullable=True,  # JSONB for plugin configuration
     )
 
     # Transient attribute for response (not persisted)