feat: Active Fraud Proof Watchtower & Sequencer Reputation (Phase 7) 🏮

[intelliDean]

Phase 7: Active Fraud Proof Watchtower & Sequencer Reputation

This PR transitions FlashStat from a passive monitoring tool to an Active Network Defense System.

🛠️ Key Implementation Details:

1. Active Fraud Proof Watchtower:
   • Implemented RLP-encoded proof generation for DoubleSpend and Equivocation events using ethers::utils::rlp.
   • Developed a GuardianWallet that supports automated on-chain transaction signing.
   • Integrated autonomous slashing triggers into the FlashMonitor loop.
2. Sequencer Reputation System:
   • Added cumulative tracking for TEE-attested blocks and Stability Streaks.
   • Implemented a refined scoring engine:
     • +1 per block signed.
     • +1 per TEE-attested block (cumulative).
     • +10 per 100-block stability streak.
     • -1000 slash for equivocations.
3. Observability & Reliability:
   • Refactored FlashMonitor to use dependency injection for storage, fixing database lock issues in tests.
   • Added comprehensive unit tests in flashstat-core for scoring math and serialization.

🧪 Validation:

• Verified with cargo test -p flashstat-core.
• Tested end-to-end with flashstat-simulate injecting synthetic equivocation events.

🏮 Config Updates:

Added [guardian] section to flashstat.toml for managing the slashing contract and security parameters.