AlgoScan

The examples/nft/* programs require `["nft", "algod"]`; with `nft` off by
default, the default clippy/check/test runs skipped them. Add `--features
nft` to the steps that compile examples:

- Makefile: `clippy` and `test` targets (so `make ci` builds and lints them).
- CI (general.yml): `cargo-check`, `cargo-clippy`, `cargo-test` jobs.

`nft` is additive (default-off), so enabling it on the --all-targets /
--examples steps is strictly more coverage and cannot mask a default-build
breakage. The wasm-check job stays default.

Organize every example under examples/<category>/ — client, contract,
app, asset, transaction, account, logic_sig, wallet, nft — with explicit
[[example]] path entries. The example `name` is unchanged, so
`cargo run --example <name>` keeps working.

Move the NFT examples out of algonaut_nft/examples and into examples/nft,
and rewrite them against a live algod instead of mocking: real
suggested_params, submit, and real asset ids returned from the network
(no DemoParams stub, no hardcoded AssetId). Gated on
required-features = ["nft", "algod"]:
- nft_mint_arc3   — pure NFT, ARC-3 off-chain metadata
- nft_mint_arc19  — mutable NFT; mint then UpdateAsset the reserve
- nft_mint_arc69  — on-chain metadata in the acfg note
- nft_soulbound   — full ARC-71 issue/hold/revoke across issuer + funded holder
- nft_arc89_box   — mint for a real id, build the ARC-89 box offline

Redesign the asa module around a fluent NftMint builder and make the
crate's API idiomatic, then add runnable examples that lead the UX.

asa:
- Replace the leaky create_pure_nft / create_fractional_nft free
  functions (which returned a half-built CreateAsset and told the caller
  via doc comment to attach url/hash/reserve themselves) with NftMint.
  NftMint::pure/fractional own the configuration; .arc3() computes the
  ARC-3 metadata hash and appends #arc3, .arc19() derives the reserve
  from a CID, .arc69() places metadata in the note. Terminals return a
  finished CreateAsset (into_create) or Transaction (build).
- Make the NFT-shape predicates an extension trait (NftShape) so they
  read as methods on AssetParams.
- Rework the ARC-71 Soulbound typestate so Held/Revoked carry the
  AssetId; claim/revoke are now total (no Option, no unwrap).

url: Cid and TemplateIpfsUrl gain Display / FromStr; reserve derivation
is now `impl From<Cid> for Address`; the free parse/render/convert
functions become methods.

arc89: add with_* flag setters so callers never poke raw flag bytes.

lib: ZERO_ADDRESS is a const (was a fn); add a curated prelude.

examples/: mint_pure_nft, mint_mutable_arc19, mint_onchain_arc69,
soulbound_credential, resolve_metadata, arc89_preview — each builds and
runs, demonstrating the new ergonomics end to end.

No backward-compat concerns: the crate is unreleased.

Introduce algonaut_nft, an offline-first workspace crate covering the
NFT-related ARCs, and record/accept the design in
docs/adr/algonaut-nft-subcrate.md.

Coverage:
- ARC-3 / ARC-69 metadata models (off-chain JSON and acfg-note), with
  ARC-16 traits and ARC-36 filters and ARC-53 collection declarations.
- ARC-3 integrity: the `am` hash (plain SHA-256 and the domain-separated
  SHA-512/256 form) and SRI `*_integrity` strings.
- ARC-19 template-ipfs <-> reserve-address transform, with a self-
  contained CID v0/v1 (base58btc + base32) codec.
- ARC-71 soulbound (non-transferable ASA) lifecycle as a typestate, plus
  pure/fractional NFT ASA presets over the existing asset builders.
- ARC-72/ARC-73 smart-contract NFT ABI signatures, selectors and
  interface ids, and ARC-18 royalty-enforcer bindings.
- ARC-74 indexer request/response types, with an async client behind the
  opt-in `fetch` feature.
- ARC-89 preview: an offline, byte-exact Asset Metadata Box codec, flag
  bytes, domain-separated hash, and registry constants (marked unstable).

The offline core links no HTTP client; the ARC-74 client and metadata
fetch ride algonaut_nft's `fetch` feature. The umbrella re-exports it as
`algonaut::nft` behind an additive, default-off `nft` feature (plus
`nft-fetch`), so existing builds are unchanged. No backward-compatibility
guarantees apply while the crate stabilises.