@decocms 6.x → 7.x Split-Package Upgrade (TanStack sites)

Moves a TanStack Start site off the two monoliths onto the split packages:

• @decocms/start@6.x → @decocms/blocks (framework core), @decocms/tanstack (TanStack binding), @decocms/blocks-admin (admin/preview), @decocms/blocks-cli (generators + migration tooling, devDep)
• @decocms/apps@5.x → per-vendor @decocms/apps-* — add only the splits the site actually imports

Proven on three production storefronts: lebiscuit-tanstack (commits 73daa3b → b5fdf69 → 6d311d8, the canonical sequence), miess-01-tanstack (PR #86), granadobr-tanstack (PR #69). Target ^7.6.0 at minimum; ^7.7.0 removes two workarounds (noted below).

The commit sequence

Do this as three separate commits in this order — each leaves the repo in a reviewable, explainable state, and the typecheck-baseline diff (see Verification) is only meaningful per-step.

Commit 1 — dependency swap

Remove: