Replace address_structure_stats with address_maad_stats: one rowid row per
scope, side and measure with REAL dimensions, INTEGER metadata, and tau,
tau_sd and spectrum as little-endian f32 blobs. The q grid is stored once in
maad_q_grid. Verify checks blob lengths against the grid and spectrum presence
per measure; compare checks f32 arrays element-wise within the MAAD tolerance.
Bumps the product schema to 7 and the MAAD contract to 6.