feat: migrate deployment to Hardhat Ignition

Replace the imperative deploy scripts with Hardhat Ignition modules:
- ignition/modules/{MockToken,Reputation,P2PIX}.ts orchestrate the full
  deployment graph; P2PIX.ts wires MockToken + Reputation and deploys
  P2PIX via its constructor
- ignition/parameters/localhost.json holds per-network values
  (defaultBlocks, validSigners, MockToken supply)
- swap hardhat-toolbox for the individual plugins that Ignition needs;
  add hardhat-verify (v2) and bump hardhat/hardhat-tracer accordingly
- delete scripts/1-deploy-mockToken.ts and scripts/2-deploy-p2pix.ts
- add deploy:{localhost,goerli,sepolia,mumbai} npm scripts
- include ignition/**/* in tsconfig.json
- gitignore ignition/deployments/chain-31337/ (ephemeral local state)

This branch carries the deployment-tooling migration only — the contract
is still the original constructor-based P2PIX. Proxy / UUPS deploy
support will land alongside the upgradeable contract change.

ignition/parameters/localhost.json

@@ -0,0 +1,9 @@
+{
+  "P2PIX": {
+    "defaultBlocks": 10,
+    "validSigners": []
+  },
+  "MockToken": {
+    "supply": "20000000000000000000000000"
+  }
+}