v0.3.0 - Milestone 3

Milestone 3 of the Canton dev-fund grant (#407): the token standard in both versions (CIP-56 V1 and CIP-0112 V2), interactive submission with a pluggable signer, a typed PQS client, the conformance suite mapped to the Ledger Client Standard with its compatibility matrix, and the remaining canton-splice-* crates. All 31 crates are on crates.io at 0.3.0.

New crates: canton-token, canton-signer, canton-pqs, canton-daml-stdlib, the thirteen canton-splice-api-token-* crates (one per Splice token-standard package, V1 and V2) and canton-splice-api-featured-app-v1.

Two breaking changes for 0.2.x users, with the migration in the changelog: the token-standard packages are crates of their own now (a path such as canton_splice_amulet::splice_api_token_holding_v1::… becomes canton_splice_api_token_holding_v1::…, with that crate added to Cargo.toml), and Error::Http gained a url field.

Verified on a cn-quickstart LocalNet, on a Canton Builder Tool LocalNet, and on the Canton Network DevNet (Canton 3.5.17, Splice 0.8.1): the V1 and V2 transfers, a V2 allocation withdrawn and another settled by its executor, every DevNet update id read back from the participant. The runs are on record in docs/verification/token-standard-live-runs.md.

The complete list of changes is in CHANGELOG.md.