feat(eip712): enable canonical structured review without blind signing

[BitHighlander]

Enables canonical device-driven structured EIP-712 review for 7.16 without Advanced Mode.

• The device requests each struct/value, validates it, displays it, and hashes those same bytes.
• The legacy whole-JSON parser remains disabled.
• Precomputed typed hashes remain blind-signing operations gated by Advanced Mode.
• Canonical identifier checks prevent truncation, control characters, and duplicate member ambiguity.
• Pins the matching Python hardware/reference harness.

Local evidence:

• Exact clang-format 20 gate passes.
• Pinned Docker emulator/debug build passes.
• 545/545 firmware tests pass, plus board and crypto suites.
• Published EIP-712 Mail hashes, Permit2, ERC-2612, nested structs, arrays, and adversarial cases remain covered.

Depends on the Python harness PR from feat/716-structured-eip712-no-advanced.

[BitHighlander]

Readiness update: this feature line is included in coherent alpha roll-up #625. Merging #611 and #619 independently would make their single deps/python-keepkey gitlink updates overwrite one another; #625 resolves that integration boundary with unified companion PR #63. Keep this PR open until #625’s exact-head matrices finish; if #625 merges, close this PR as subsumed rather than merging it separately.

[BitHighlander]

GitHub marked this PR merged when #625 landed at 03:04:58Z because this head is contained in #625 ancestry. Operational disposition: subsumed by #625; do not repin to this PR’s former standalone companion gitlink.