[Bug]: Missing Unit Tests for VolunteerManage (volunteermanage.py) #5188

Description

Summary

esp/esp/program/modules/handlers/volunteermanage.py manages volunteer requests, imports, and scheduling flows, but it has no dedicated tests in the module test suite.

Why this matters

This module includes:

• volunteer request form handling
• volunteer import behavior
• admin-only workflow management
• CSV/file-based operations
• interactions with volunteer signup data and event/timeslot models

These are multi-branch behaviors with user-facing and admin-facing side effects.

Suggested test coverage

Add tests for:

• the volunteer management landing flow for admins
• volunteer request creation/update behavior
• volunteer import validation and processing
• handling of invalid imports or malformed rows
• expected redirects and rendered messages after actions

Acceptance criteria

• A dedicated test module is added
• Tests cover both manual form flows and import flows
• Tests verify side effects on volunteer requests or related models