chore(codegen): drop committed src/blockchain/abi.ts in favor of generated src/generated.ts

The 58KB src/blockchain/abi.ts was the output of the legacy hardhat-based
wagmi config and was being committed verbatim. Since wagmi.config.ts now
emits src/generated.ts (gitignored, regenerated on every prestart via
`bun run wagmi:gen`), keeping the old artifact in the tree was just dead
weight.

- Remove src/blockchain/abi.ts from tracking
- Repoint 4 imports (sellerMethods, events, provider, BuyerSearchComponent)
  from `@/blockchain/abi` / `./abi` to `@/generated`
- contracts:compile now injects ALCHEMY_API_KEY=placeholder + a default
  test MNEMONIC so hardhat.config.ts can load without a manual .env in
  the submodule (matches the placeholder values used in p2pix-front-end's
  submodule .env)

src/components/BuyerSteps/BuyerSearchComponent.vue

@@ -12,7 +12,7 @@ import { onClickOutside } from '@vueuse/core';
 import { Networks } from '@/config/networks';
 import { TokenEnum } from '@/model/NetworkEnum';
 import { getContract } from '@/blockchain/provider';
-import { reputationAbi } from '@/blockchain/abi';
+import { reputationAbi } from '@/generated';
 import { type Address } from 'viem';
 
 // Store reference