BitBox02 firmware

This commit adds a new memory flag that records which password-stretching algorithm was used to protect the wallet seed. It does not change the actual stretching math yet; it only stores the choice so future firmware can support a newer algorithm while still recognizing older backups. There is no immediate security fix, but it is infrastructure for a future security improvement.

This commit is a code cleanup and test-improvement change. It moves two device-attestation helper functions from a direct hardware call into a software 'hardware abstraction layer' (HAL) so the code can be tested without the real device. It also adds unit tests that simulate the attestation process. There is no indication this fixes a security bug or introduces a new vulnerability.

This commit only adds Apache-2.0 license header comments to 16 source files that were missing them. It makes no functional changes to the BitBox02 firmware or its Python tools. There is no security impact.

This commit is a bulk license-header cleanup. It replaces long, multi-line copyright and Apache-2.0 license notices at the top of 429 source files with a single, standardized machine-readable tag: 'SPDX-License-Identifier: Apache-2.0'. No program logic, build rules, or file contents other than the header comments were changed. It does not introduce or fix any security vulnerability.

This commit only updates copyright years in two LICENSE files. It makes no changes to software code, functionality, or security controls. There is no security relevance.

This commit is a routine code-style fix. It updates the Python formatter (black) configuration so the linter uses the correct pyproject.toml file, and reformats two Python files to match the new style rules. There are no security changes to the firmware or any sensitive logic.

This commit only fixes a typo in a code comment (docstring). It changes the description of when a function can return an error, matching the fact that the function now receives the private key directly rather than fetching it from a locked keystore. No actual code behavior is changed.

This commit is a routine code cleanup. It removes a locally defined constant for compressed secp256k1 public key size (33 bytes) and replaces it with an equivalent constant already provided by the upstream Rust bitcoin/secp256k1 library. The numeric value and behavior remain exactly the same.

This commit removes an unused header file called keystore.h and updates the code that previously included it. The two constants that were defined in that header (KEYSTORE_U2F_SEED_LENGTH and XPUB_ENCODED_LEN) are no longer referenced through the header. In the U2F code, the seed length is now taken directly from the size of the local seed variable using sizeof(seed), which is functionally equivalent because the seed is a fixed-size array of the same length. There is no security-relevant change here—this is a cleanup refactor.

This is a small internal cleanup in the BitBox02 firmware's on-screen text input component. A helper function that fetches BIP39 seed words was simplified so callers no longer check its return value; the helper itself now aborts on failure. There is no security vulnerability here—just a minor code-style refactor that keeps the same failure behavior.

This commit removes an old C source file called keystore.c and moves two small cryptographic helper functions directly into the Rust part of the project. The functions themselves still do exactly the same secp256k1 signing and nonce-commitment work as before; they are just called from Rust instead of going through a thin C wrapper. There is no indication this fixes or introduces a security bug.

This commit simply moves a helper function that looks up a BIP39 word by its index from one source file to another. The function's behavior and the callers' logic are unchanged; it is a code cleanup with no security impact.