v0.7.6 — fix AVL tree node persistence bug (double tree.reset())

v0.7.6 — fix AVL tree node persistence bug (double tree.reset())

BatchAVLProver::generate_proof() called tree.reset() which cleared
is_new/visited flags before VersionedAVLStorage::update() could use
them to persist changed nodes. Internal nodes created during AVL
rebalancing were silently dropped from storage, causing resolver-miss
panics at tip. Fixed upstream in ergo_avltree_rust (3dc6a06).

State built under prior versions has missing nodes permanently —
nuke state.redb and resync after upgrading.

Full Changelog: v0.7.5...v0.7.6