fix: replace deprecated Plex v1 invite endpoints with v2 API for auto-accept

[engels74]

Summary

• Replace plexapi's deprecated v1 invite endpoints (/api/invites/requests, which now return 410 Gone) with direct HTTP calls to the Plex v2 API (/api/v2/shared_servers/invites/received/pending and /api/v2/shared_servers/{id}/accept)
• Add retry logic (3 attempts, 1s delay) to handle invite propagation delay after the shared_servers POST
• Enhance logging: info level for invite status, warning level for exceptions (previously debug), and include auto_accepted in the plex_library_shared_direct log event

Context

plexapi 4.18's pendingInvites() and acceptInvite() use Plex v1 endpoints that Plex has retired (returns 410 Gone). The auto-accept block caught the resulting exception at debug level and swallowed it, causing users to need manual acceptance at plex.tv after OAuth redemption.

This is the same issue reported upstream in python-plexapi#1536, with a fix proposed in pushingkarmaorg/python-plexapi#1537 (still unmerged). The approach here mirrors how Wizarr solved the same problem.

Test plan

• 77/77 plex client property tests pass (5 new tests for v2 auto-accept)
• 548/548 full backend test suite passes
• basedpyright: 0 errors, 0 warnings
• ruff check + ruff format: clean
• Manual test: create invitation, redeem via Plex OAuth, verify auto_accepted=True in logs and immediate library access

[augmentcode]

🤖 Augment PR Summary

Summary: Updates Plex direct-share auto-accept to use Plex�s v2 invite APIs instead of plexapi�s deprecated v1 invite endpoints.

Why: Plex�s v1 invite endpoints (used by plexapi 4.18 for pending/accept) now return 410 Gone, causing auto-accept to fail and requiring manual acceptance on plex.tv.

Changes:

• Replace v1-based pendingInvites()/acceptInvite() usage with direct HTTP calls to /api/v2/shared_servers/invites/received/pending and /api/v2/shared_servers/{id}/accept
• Add retry logic (3 attempts, 1s delay) to handle invite propagation delay after shared_servers creation
• Improve observability with info-level invite status logs and warning-level exception logs (including attempt count)
• Include auto_accepted in the plex_library_shared_direct log event

Technical Notes: The new flow executes in asyncio.to_thread and adds property tests/mocks validating success, retry, and error logging behavior.

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[augmentcode]

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