Scope already-reported students by their actual batch in get_batch_students

[vikrantwiz02]

Summary

• get_batch_students builds an academic_students list (students already transferred to the main academic tables) by matching year + programme type + discipline only, never the specific batch_id
• A reported student therefore leaked into every sibling batch of the same year/discipline/programme type (e.g. a PhD Design student assigned to the Odd 2019 batch also showed up in the Even 2019 batch of the same discipline, with mostly blank fields since that entry comes from a differently-shaped source)
• Filtering on batch_id scopes the query to the specific batch being viewed

Test plan

• Verified against real data: the Even batch query returned the leaked students before the fix and correctly excludes them after, while the Odd batch (their real batch) still returns them
• Python syntax check passes