chore(codegen): keep src/blockchain/abi.ts as wagmi output + infra polish

Path revert (reduces churn / preserves existing imports):
- wagmi.config.ts: out -> src/blockchain/abi.ts (was src/generated.ts)
- Restore the 4 import sites (sellerMethods, events, provider,
  BuyerSearchComponent) to import from './abi' / '@/blockchain/abi'
- .gitignore: ignore src/blockchain/abi.ts (was src/generated.ts)

The file keeps its original location and is no longer committed — it is
regenerated from the smart-contracts submodule artifacts on every
prestart via `bun run wagmi:gen`.

Infra polish:
- package.json: contracts:compile uses pushd/popd (instead of cd) so the
  shell returns to the project root after the submodule build, even when
  the script is the leaf of a longer chain
- .gitmodules: zkPix submodule pinned to `dev`

package.json

@@ -13,7 +13,7 @@
     "lint:fix": "eslint . --fix",
     "format": "prettier --write \"src/**/*.{ts,vue,json}\"",
     "format:check": "prettier --check \"src/**/*.{ts,vue,json}\"",
-    "contracts:compile": "cd p2pix-smart-contracts && bun install && ALCHEMY_API_KEY=placeholder MNEMONIC='test test test test test test test test test test test junk' bunx hardhat compile",
+    "contracts:compile": "pushd p2pix-smart-contracts && bun install && ALCHEMY_API_KEY=placeholder MNEMONIC='test test test test test test test test test test test junk' bunx hardhat compile && popd",
     "prewagmi:gen": "bun run contracts:compile",
     "wagmi:gen": "bun ./node_modules/@wagmi/cli/dist/esm/cli.js generate"
   },