fix(circuit_breaker): remove anonymous failure reporting and restore Sybil resistance (closes #313)

[guptakumarranjeet150]

Summary

Closes #313

Closes the anonymous failure-counter path in batch dispatch by requiring attributable reporter signatures and routing `BatchCall::RecordFailure(reporter)` through `record_failure(env, reporter)`. This restores the documented anti-DoS Sybil barrier (`MAX_REPORTS_PER_REPORTER * (MIN_DISTINCT_REPORTERS - 1) <= FAILURE_THRESHOLD`) preventing unauthenticated callers from manipulating the circuit-breaker state.

Key Changes

• Batch Dispatch Attribution (`src/types.rs`, `src/contracts/proxy_entry/mod.rs`):
  • Updated `BatchCall::RecordFailure(Address)` to carry an attributable reporter address.
  • Routed dispatch through authenticated `Self::record_failure(env, reporter)` which validates the address and enforces signature authorization.
• Removed Unauthenticated Path (`src/circuit_breaker.rs`):
  • Deleted `record_failure_anonymous` which previously bypassed authentication, quotas, and cooldowns.
  • Made `pub mod circuit_breaker` in `src/lib.rs` to expose security parameters for audit and test assertions.
• Unit & Regression Testing (`tests/circuit_breaker_dos.rs`):
  • Updated `test_batch_execute_with_record_failure_variant` asserting attributable batch execution.
  • Added `test_sybil_barrier_arithmetic_invariant` verifying the anti-DoS arithmetic invariant.
  • Added `test_batch_execute_record_failure_requires_auth` asserting that unauthenticated callers on the batch path cannot increment `FailureCount`.

Verification

• `cargo test --test circuit_breaker_dos`: 17/17 tests passing green.
• `cargo test --lib`: 15/15 tests passing green.