fix(models): add explicit enum names to match migration types

SQLAlchemy's Enum() auto-generates type names from Python class names
(e.g., AutonomyLevel -> autonomylevel), but migrations defined them
with underscores (e.g., autonomy_level). This mismatch caused:

  "type 'autonomylevel' does not exist"

Added explicit name parameters to all enum columns to match the
migration-defined type names:
- autonomy_level, project_status, project_complexity, client_mode
- agent_status, sprint_status
- issue_type, issue_status, issue_priority, sync_status

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

backend/app/models/syndarix/sprint.py

@@ -57,7 +57,7 @@ class Sprint(Base, UUIDMixin, TimestampMixin):
 
     # Status
     status: Column[SprintStatus] = Column(
-        Enum(SprintStatus),
+        Enum(SprintStatus, name="sprint_status"),
         default=SprintStatus.PLANNED,
         nullable=False,
         index=True,