fix(sync): preserve subscriptions from other semesters

[tiankaima]

Root cause

school sync combined all matched sections into one global action=set request. The server historically interpreted that request as replacing every subscribed section, so syncing a subset of semesters could erase historical subscriptions used by Dashboard, Bot schedules, homework history, and iCalendar.

This is the CLI side of Life-USTC/server#431 and depends on the semester-scoped server behavior in Life-USTC/server#434.

Changes

• Group matched section IDs by Life@USTC semester.
• Send one action=set request per semester with semesterId populated.
• Preserve the existing aggregate output and skip empty/unmatched semester updates.
• Add a unit test that locks the semester-scoped request payload.

Validation

• gofmt
• go test ./...

[tiankaima]

CI exposed that cli/main generated OpenAPI files were behind the current Server schema. I synced the generated client and updated the two ListUploads call sites for its new optional params argument. go test ./... and a second generation pass are clean locally; waiting for the rerun.