feat: generate frontend ABI bindings from Hardhat artifacts (ticket 09)

[knzeng-e]

Ticket 09: generate frontend ABI bindings from Hardhat artifacts

Stops the frontend hand-maintaining contract ABIs. A small Node script reads the
Hardhat artifacts and emits viem-typed as const modules; the frontend imports
those, and CI fails if they drift from the compiled contracts. Branches from main.

What this does

• contracts/evm/scripts/generate-abis.mjs: reads the artifacts and writes
  web/src/generated/contracts/<name>.ts (+ an index.ts barrel), each with an
  // Auto-generated. Do not edit manually. header. Plain Node ESM on purpose:
  it only reads artifact JSON, so no ts-node or Hardhat runtime is needed.
• npm run generate:abis (in contracts/evm) = hardhat compile && node scripts/generate-abis.mjs.
• Covered contracts (the ones the app calls): ArtistDirectory,
  ArtistRuntimeFactory, and the MusicRegistry / MusicRoyalties / MusicAccess
  / MusicNFT pallet facets. SmartRuntime is a diamond and is called through
  those facet ABIs at the runtime address, so it needs no separate binding;
  extend CONTRACTS in the script to add more.
• web/src/shared/config/contracts.ts drops its six hand-maintained ABI blocks
  and re-exports the generated modules under the same names, so useCatalog and
  useArtistConsole are unchanged. The generated (full) ABIs are supersets of the
  previously curated subsets.
• Generated files are committed, excluded from ESLint/Prettier (machine
  output) but still typechecked by tsc, so an un-regenerated signature change
  fails the web build.
• ci-evm regenerates and runs git diff --exit-code -- web/src/generated to
  fail on drift; its path filter now also watches web/src/generated/**.
• Docs: web/README workflow section, ticket 09 delivery notes, backlog + plan status.

Acceptance criteria (ticket 09)

• Fresh clone can compile contracts and generate bindings: yes (npm run generate:abis).
• Frontend builds using generated bindings: yes.
• Contract signature changes produce visible TS/CI failures: yes (tsc on the
  committed modules + the ci-evm drift diff).
• Documentation explains the workflow: yes.

Verification

generate:abis clean (byte-stable output), then in web/: tsc + lint (0 errors)

• build + fmt:check + 72 unit tests + 10/10 Playwright e2e, all green. Behavior
  unchanged (the e2e specs drive the on-chain calls through the new ABIs).

🤖 Generated with Claude Code

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