[meta] Track cleanup and implementation of known v0.2.0 limitations

This issue tracks the known limitations of the `v0.2.0` release, as outlined in the release notes. These include compiler warnings, placeholder methods, and incomplete MEV strategy or relay support.

The goal is **not** just to silence warnings, but to either:
- Complete the underlying implementation
- Remove unused scaffolding
- Or explicitly annotate intentional dead code with `#[allow(dead_code)]` and `TODO` comments

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### ⚠️ Current Known Limitations

#### 📦 `MEVBundle` struct
- [ ] `min_timestamp`, `max_timestamp`, `total_gas` are unused

#### 🌐 `RelayConfig` struct
- [ ] `endpoint` and `signing_key` not yet used

#### ✅ Validation
- [ ] `validate_bundle()` is defined but never called

#### 💰 `TxType` enum
- [ ] `ERC20Transfer` fields `token`, `amount` unused
- [ ] Variants `CompoundSupply` and `AaveBorrow` not constructed anywhere

#### 📊 `MEVMetrics` methods
- [ ] `record_transaction()`, `record_opportunity()`
- [ ] `record_bundle_submission()`, `record_bundle_inclusion()`

#### ⚙️ `Config` struct
- [ ] `from_env()` and `validate()` are unused

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### 📌 Suggested Resolution Paths

Each item should be evaluated case-by-case:
- If planned for future use → document with `#[allow(dead_code)]` and inline `TODO`
- If obsolete or speculative → remove to reduce noise
- If ready to implement → break into smaller, focused issues

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### 🔗 Related Issues

- (Will be linked here when created)

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### 🧭 Goal

Track cleanup and/or completion of features scaffolded in `v0.2.0`, setting the stage for a cleaner and testable `v0.3.0`.