Function apply_block_moved 

fn apply_block_moved(
    wstore: &WaveStore,
    block_id: &str,
    src_tab_id: &str,
    dst_tab_id: &str,
    dst_index: u32,
) -> Result<(), Box<dyn Error>>

Phase E.5.5 — apply a BlockMoved event to SQLite. Handles both cross-tab moves and intra-tab repositioning. Idempotent on re-delivery (checks current parent before mutating).