Cardano Updates

chore: release 3.0.0

@types/node should match the oldest supported Node line (engines >=20.19),
not the newest. v25 types describe APIs absent on Node 20, which would
type-check but be undefined at runtime. Pin to ^20.19.43.

Co-Authored-By: Claude Opus 4.8 (1M context) <[email protected]>

Node 18 is below the new >=20.19 engines floor (and ESLint 10 / Vite 8
won't run on it). Also modernize the workflow actions and fix the Yarn 4
install flag.

- build.yml: matrix 18.x/20.x -> 20.x/22.x/24.x; checkout@v2 -> v4,
  setup-node@v1 -> v4
- release.yaml: node 18 -> 20; checkout/setup-node -> v4;
  yarn install --frozen-lockfile -> --immutable (Yarn 4 syntax)

Co-Authored-By: Claude Opus 4.8 (1M context) <[email protected]>

Upgrade all dependencies to their latest versions, including majors.

Runtime:
- @emurgo/cardano-serialization-lib-nodejs 11 -> 15 (migrate PlutusMap.get
  which now returns PlutusMapValues)
- cbor 9 -> 10, yaml 2.3 -> 2.9

Dev toolchain:
- ESLint 8 -> 10 (migrate .eslintrc.js -> flat eslint.config.mjs)
- TypeScript 5 -> 6, Vitest 0.32 -> 4, Prettier 2 -> 3, Fastify 4 -> 5
- Yarn 4.5 -> 4.17 (4.5 TS compat patch can't apply to TS 6 under PnP)
- drop unused eslint-plugin-import

Other:
- raise minimum Node.js to 20.19 (ESLint 10 / Vite 8 floor)
- tsconfig: target/lib ES2022, add rootDir + ignoreDeprecations
- fix NodeJS.Timer -> NodeJS.Timeout for @types/node 25
- remove unused pm2Metrics (never exported)

Co-Authored-By: Claude Opus 4.8 (1M context) <[email protected]>