feat(popkins): Local Devnet with Anvil + popsigner-lite for offline development

### 📋 Summary

Implement a zero-dependency local development environment for both **OP Stack** and **Nitro** rollups. Developers can run a complete rollup on their local machine without connecting to Ethereum, Celestia, or POPSigner Cloud.

---

### 🎯 Goals

- `docker compose up` experience for local rollup development
- Works completely offline (airgapped)
- Same binaries as production
- Clear upgrade path from local → testnet → mainnet
- **Applies to both OP Stack and Nitro** (same architecture, different rollup configs)

---

### 🏗️ Components to Build

Build in this order - each step depends on the previous:

| # | Component | Description |
|---|-----------|-------------|
| 1 | **`popsigner-lite`** | Minimal signing service with Anvil's 10 deterministic keys. Same JSON-RPC interface as production POPSigner (`eth_signTransaction`, `health_status`, `opsigner_signBlockPayload`). No auth, no DB, no OpenBao. ~200 lines Go. **This unblocks everything else.** |
| 2 | **`mock-celestia / localestia`** | Mock Celestia node with gRPC (9090) + JSON-RPC (26658). In-memory blob storage, instant finality, state dump/load. ~500 lines Go. **Required for OP Stack with Alt-DA.** |
| 3 | **Anvil State Generator (OP Stack)** | Backend code at `control-plane/internal/bootstrap/opstack/anvil_deployer.go`. Spins up ephemeral Anvil, deploys OP Stack contracts using existing `op-deployer` integration, dumps state via `anvil_dumpState`. |
| 4 | **Anvil State Generator (Nitro)** | Backend code at `control-plane/internal/bootstrap/nitro/anvil_deployer.go`. Same pattern - deploy Nitro contracts (`RollupCreator`, etc.) to Anvil, dump state. **Mirror the working OP Stack implementation.** |
| 5 | **Local Docker Compose Templates** | Generate `docker-compose.yml` for local devnet. Two templates: one for OP Stack (Anvil + mock-celestia + popsigner-lite + op-* binaries), one for Nitro (Anvil + popsigner-lite + nitro-node + sequencer). |
| 6 | **Bundle Generator & Download** | Package everything into downloadable `.tar.gz` artifact with pre-filled `.env`, state dumps, genesis, and scripts. |
| 7 | **Dashboard UI** | Add "Local Devnet" option in chain creation wizard. Show bundle download when ready. |

---

### 🔁 Nitro Parity

The Nitro implementation should mirror OP Stack's architecture since both are already working in production:

| Concern | OP Stack (Reference) | Nitro (To Implement) |
|---------|---------------------|---------------------|
| Contract Deployer | `opstack/anvil_deployer.go` | `nitro/anvil_deployer.go` |
| Signing | popsigner-lite | popsigner-lite (same) |
| L1 Mock | Anvil | Anvil (same) |
| DA Mock | mock-celestia | N/A (Nitro uses L1 calldata or AnyTrust - not in scope for local) |
| State Dump | `anvil_dumpState` | `anvil_dumpState` (same) |

---

### 🔑 Key Assignments (Anvil's Deterministic Keys)

| Role | Address | Private Key |
|------|---------|-------------|
| Deployer | `0xf39Fd6e51aad88F6F4ce6aB8827279cffFb92266` | `0xac09...ff80` |
| Batcher | `0x70997970C51812dc3A010C7d01b50e0d17dc79C8` | `0x59c6...690d` |
| Proposer | `0x3C44CdDdB6a900fa2b585dd299e03d12FA4293BC` | `0x5de4...365a` |
| Admin | `0x90F79bf6EB2c4f870365E785982E1f101E93b906` | `0x7c85...07a6` |

Use publicly known keys

---

### 📦 Bundle Structure

```
my-local-rollup-devnet/
├── docker-compose.yml
├── .env # Pre-filled (not a template!)
├── state/
│ ├── anvil-state.json # L1 with deployed contracts
│ └── celestia-state.json # OP Stack only
├── genesis/
│ └── genesis.json
├── config/
│ ├── rollup.json # OP Stack: rollup.json, Nitro: nodeConfig.json
│ ├── addresses.json
│ └── jwt.txt
├── scripts/
│ ├── start.sh
│ ├── stop.sh
│ └── reset.sh
└── README.md
```

---

### 🌐 API Changes

**New deployment option:**
```json
POST /api/v1/deployments
{
"chainType": "opstack", // or "nitro"
"targetEnvironment": "local", // NEW
"name": "my-local-rollup",
"l2ChainId": 42069
}
```

**CLI support:**
```bash
popctl bootstrap create --name my-rollup --chain-type opstack --target local --download ./my-rollup/
popctl bootstrap create --name my-rollup --chain-type nitro --target local --download ./my-rollup/
```

---

### ✅ Success Metrics

| Metric | Target |
|--------|--------|
| Bundle generation time | < 60 seconds |
| Bundle size | < 20 MB compressed |
| Time to first L2 block | < 30 seconds after `docker compose up` |
| Works offline | 100% |

---

### ✅ In Scope (from PRD)

**Backend:**
- [ ] `popsigner-lite` Docker image with Anvil keys pre-loaded
- [ ] `mock-celestia` Docker image with blob storage + state dump/load
- [ ] `anvil_deployer.go` for OP Stack - ephemeral Anvil + contract deployment + state dump
- [ ] `anvil_deployer.go` for Nitro - same pattern
- [ ] Local Docker Compose template generation (different from production templates)
- [ ] Bundle packaging: `.tar.gz` with pre-filled `.env`, state dumps, genesis, scripts
- [ ] New API: `POST /api/v1/deployments` with `targetEnvironment: "local"`
- [ ] New API: `GET /api/v1/deployments/{id}/bundle` to download `.tar.gz`

**Dashboard:**
- [ ] "Local Devnet (Anvil)" option in target environment selector
- [ ] Bundle download button when generation completes
- [ ] Quick start instructions in deployment details page
- [ ] Clear "No funding required" messaging for local devnet

**CLI (popctl):**
- [ ] `--target local` flag for `bootstrap create`
- [ ] `--download ` option to save bundle directly

**Bundle Contents:**
- [ ] `docker-compose.yml` - ready to run, no edits needed
- [ ] `.env` - pre-filled with Anvil addresses and contract addresses
- [ ] `state/anvil-state.json` - L1 with deployed contracts
- [ ] `state/celestia-state.json` - empty initial state (OP Stack only)
- [ ] `genesis/genesis.json` - L2 genesis
- [ ] `config/rollup.json` or `nodeConfig.json` - rollup configuration
- [ ] `config/addresses.json` - deployed contract addresses
- [ ] `config/jwt.txt` - JWT secret for auth RPC
- [ ] `scripts/start.sh`, `stop.sh`, `reset.sh` - convenience scripts
- [ ] `README.md` - quick start guide with endpoints and accounts

---

### 🚫 Out of Scope (v1)

- Block explorer
- L2 faucet (Anvil accounts have unlimited ETH)
- Multiple L2 chains
- Custom key configuration