feat: fill missing thesis grade from graduation Excel (ENH-010)

[ffooll-bit]

Summary

Adds a nilai_skripsi letter-grade column to the PISN graduation Excel template and fills in a registered-but-ungraded thesis/skripsi course at submission time.

• Graduation: EXCEL_HEADERS/downloadTemplate/parseExcel recognise a 5th nilai_skripsi column (stored uppercased per student); new private findMissingGradeThesis() resolves the thesis course that is still ungraded and returns its composite key; finish() pushes the Excel value via UpdateNilaiPerkuliahanKelas only when the grade is currently missing.
• NeoFeeder: new updateNilaiPerkuliahanKelas($token, $idRegistrasi, $idKelas, $record) using sendMutation('UpdateNilaiPerkuliahanKelas', ...) with the composite key id_registrasi_mahasiswa + id_kelas_kuliah (schema verified live via GetDictionary).
• wizard.php: card 3 shows the Excel value with a "(akan diisi)" tag on an ungraded thesis row.

Related issues

Fixes #110

Checklist

• php -l passes on all modified PHP files
• npm run build succeeds and committed assets are up to date (no asset changes)
• php spark routes shows correct new routes (if routes changed) (no route changes)
• vendor/bin/php-cs-fixer fix passes (no style violations)
• vendor/bin/phpunit is green (36/36)
• No debug code: dd(), var_dump(), console.log(), print_r(), exit()
• All user inputs validated server-side
• All POST forms include csrf_field() (no new forms)
• All HTML output uses esc()
• No unrelated files changed
• CHANGELOG updated if this is a user-facing change
• Behaviour verified in the browser if UI changed (attach a screenshot if useful)

Screenshot (if applicable)

Not included — verified via Playwright (non-mutating): uploading a file with the nilai_skripsi column parses cleanly and card 3 renders the thesis row correctly.

Notes for reviewers

• The grade is pushed only when the target thesis/skripsi course currently has no grade (nilai_huruf/nilai_angka empty) and a value was provided in the Excel column; students without a value are left untouched.
• Composite key (id_registrasi_mahasiswa + id_kelas_kuliah) is sourced from the cloud transcript row returned by getCekTranskripMahasiswa (verified live on NIM 202010087).
• A deliberate live-mutation was NOT performed during verification (no Berikutnya/finish() on real data); the push path was covered by a read-only reflection check of findMissingGradeThesis() (all cases pass) and local CI.