Add a fuzzy mode to the explorer search: a non-numeric, non-full-hash query now
filters the list to cached blocks whose hash (or height text) contains the query
substring, live as you type. Backed by a new ExplorerBlockCache::searchBlocks()
(SQLite LIKE with escaped wildcards), memoized per query so it doesn't hit the DB
every frame. Exact queries still navigate precisely: a block height re-anchors
the list, and a full 64-char hash is resolved via RPC. Row clicks still open the
detail modal. Empty results show "No matching cached blocks".
Note: fuzzy matching covers cached (browsed/prefetched) blocks only — the daemon
has no partial-hash index — while exact height/hash lookups reach any block.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>