Fix 701

[w568w]

This PR:

• Adds a transaction-based cookie management to fix the concurrent in-flight requests issue.
• Fixes the parsing error where the postgraduate timetable's teacher field can be null.

Fixes #701.

[Copilot]

🔵 Needs a closer look

It changes core authentication/cookie concurrency behavior (high risk) and introduces an architectural coupling concern around exception placement that should be validated in a human review.

Pull request overview

This PR addresses Fudan authentication/session race conditions by introducing transaction-based cookie updates and epoch-aware cookie saving, preventing stale in-flight responses from overwriting newly refreshed login cookies. It also hardens postgraduate timetable parsing by handling null teacher fields and improves error surfacing when both primary/fallback operations fail.

Changes:

• Add SessionCookieCoordinator + TransactionalCookieJar and integrate them into Dio cookie interception to avoid stale Set-Cookie overwrites during concurrent re-login flows.
• Refactor Neo authentication to run login inside an isolated cookie transaction and add a “retry without login” path when the session advanced mid-flight.
• Fix PG timetable parsing when JSXM (teacher) is null, and introduce a shared FallbackException for dual-attempt failures.

File summaries

File	Description
lib/util/io/cookie_manager_fix.dart	Adds epoch-coordinated cookie handling and integrates it into TolerantCookieManager.
lib/repository/cookie/independent_cookie_jar.dart	Introduces cookie storage keys and transactional cookie snapshots for isolated login updates.
lib/repository/cookie/persistent_cookie_jar.dart	Persists cookie changes via replaceCookie and maintains debounce-based saving.
lib/repository/fdu/neo_login_tool.dart	Uses transactional login cookies for Neo auth and adds epoch-based retry behavior for concurrent requests.
lib/widget/libraries/error_page_widget.dart	Adds FallbackException and renders combined primary/fallback failure messages/details.
lib/widget/dialogs/login_dialog.dart	Switches to throwing FallbackException on dual login-method failures.
lib/repository/fdu/postgraduate_timetable_repository.dart	Wraps primary/secondary timetable endpoint failures into FallbackException.
lib/model/time_table.dart	Handles nullable PG teacher field by emitting an empty teacherNames list.

Review details

• Files reviewed: 8/8 changed files
• Comments generated: 2
• Review effort level: Lite

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[w568w]

@copilot Are you stupid?

[w568w]

User confirmed that it works.