fix: skip malformed list entries instead of crashing the whole list - #4141

Summary

While looking at #4122 and #4136 (two recent crash reports with the exact error text "Cannot read properties of undefined (reading 'status')" / "(reading 'id')"), I found that every provider's list-loading code (prepareData) destructures each raw list entry's nested fields unconditionally (el.media.id, el.list_status.status, el.show.ids, etc.), with no guard for malformed/incomplete entries. AniList in particular can return mediaList entries with a null media node, and a local-storage record can end up undefined after a partial/corrupted write. A single such entry currently throws and takes down the entire list render (bookmarks grid, tracking widgets) instead of just being skipped.

Important caveat: I have not been able to conclusively confirm that this is the exact crash behind #4122/#4136 — I tried decoding the minified background-console stack trace from #4136's screenshot against a matching build, but byte offsets in a 292KB minified bundle shift with every commit, so I can't verify it lines up with confidence. I'm not claiming "fixes" those issues (not using the auto-close keyword on purpose) — this is a real, independently-verifiable class of bug worth hardening regardless, but maintainers/reporters should confirm whether it actually matches their repro before closing those reports.

Changes

Same defensive pattern applied consistently across all list providers - skip the malformed entry (con.error + continue) instead of letting one bad record crash the whole list:

• AniList/list.ts: skip entries with a missing/null media node; also guard res.data.Page before use (same crash shape as the earlier Cannot read properties of undefined (reading 'Page') #3755/Cannot read properties of undefined (reading 'Page') on Anilist in list sync page #3756 reports) so an unexpected/malformed API response throws a clear, catchable error instead of a raw property-access crash.
• Local/list.ts: skip falsy entries when iterating the local sync store.
• MyAnimeList_api/list.ts: skip entries missing node/list_status.
• Kitsu/list.ts: skip entries with missing list/el/attributes.
• Simkl/list.ts: skip entries missing show.
• Shikimori/list.ts: skip entries with no matching metadata.
• MangaBaka/list.ts: skip entries missing Series (in both prepareData and the fire-and-forget cacheList).

Test plan

• Added test/src/provider/AniList/list.test.ts and test/src/provider/local/list.test.ts covering the null-media / malformed-entry skip behavior.
• npm run test:ts:ci — all 929 tests pass (927 pre-existing + 2 new).
• npm run lint:script:ci — no new lint errors introduced.
• tsc --noEmit on both tsconfig.json and tsconfig.node.json — no new type errors.
• Not verified against the actual reported crash (see caveat above) — would appreciate a reporter or maintainer confirming/refuting against Sign in and authentication issue #4122/Extension crashing #4136 before relying on this as the fix for those specific issues.