Rework fallback for uploads with uuid

[GianniCarlo]

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[github-actions]

✅ Claude PR Review — PASS

This PR refactors LibraryDB's move/rename/promote flows into a single parameterized rewriteKeyPrefix subtree-rewrite primitive, adds an upload uuid-fallback (moveUploadTarget/moveItemToKey) so a client re-uploading a locally-moved item is treated as a move instead of tripping the uuid unique index, and routes all S3 relocation through the shared processMovedFiles helper. Authorization is sound: every new and refactored query is scoped by user_id derived from req.user.id_user, and no client-supplied id is trusted, so no IDOR is introduced. All raw SQL uses ? placeholders with no user-input interpolation, and the new escapeLikePrefix actually hardens the prior unescaped LIKE matching (a folder like My_Books can no longer capture MyXBooks). The changed routes remain behind checkSubscription/requireCloudData, no secrets or destructive migrations are present, and the change is backed by comprehensive characterization tests. No blocking issues found.

Findings: no findings

_{Model claude-opus-4-8 · run log · 0 new · 0 carried over · 1 resolved · advisory (a human should still review). Duplicate findings are de-duplicated and stale ones auto-resolved across pushes.}