Upgrade loco examples to loco-rs 1.0 (#3152)

loco-rs 1.0 depends on sea-orm 2.0, so the SeaQL/loco fork patch is no
longer needed and is dropped from all four examples.

- loco-rs 0.16 -> 1.0 in loco_example, loco_seaography, loco_starter and
  react_admin/backend, plus their migration crates
- remove the loco-rs [patch.crates-io] entry; only the sea-orm path
  patches remain
- rust-version 1.85.0 -> 1.94.0 to match loco 1.0's MSRV and the root
  workspace

No source changes required; loco 1.0 is API compatible for what these
examples use.