Add ML-KEM and ML-DSA support

[aidangarske]

ML-KEM (FIPS 203) and ML-DSA (FIPS 204) via wolfSSL backend.

Algorithms: ML-KEM-512/768/1024, ML-DSA-44/65/87

Opt-in: ./scripts/build-wolfprovider.sh --enable-pqc (adds --enable-mlkem --enable-dilithium --enable-experimental to wolfSSL). wolfProvider auto-detects from wolfSSL's options.h macros; older wolfSSL builds skip the PQC paths cleanly with no code changes here.

Validation: three independent paths cross-checked, all pass.

• Internal unit tests (11 functions x 3 levels = 33 assertions) in make test
• wolfProvider <-> OpenSSL 3.5 default provider (12 cross-pairs)
• wolfProvider <-> wolfSSL direct wc_* API (12 cross-pairs)

CI: new wolfssl-versions-pqc.yml runs three matrix rows -- pre-PQC wolfSSL, latest stable, master -- and the three-way interop validator on the PQC-enabled rows.

Test plan

• make test passes (all 11 PQC tests + existing suite)
• ./test/pqc_interop.test -- ALL PASS (24 cross-pairs)
• Build against pre-PQC wolfSSL: PQC code paths skip, make test clean
• CI green on all three matrix rows