fix: address 11 accepted security audit findings

[Lchangliang]

CRITICAL:

• GAPTOS-001: fix NewEpochEvent serialization (serde_json → bcs)

HIGH:

• GAPTOS-003: restore on-chain RandomnessConfigSeqNum read, remove hardcoded 0
• GAPTOS-004: replace unwrap() with ? in validator set deserialization
• GAPTOS-005: filter invalid validators with warning instead of panic in DKG
• GAPTOS-006: replace panic!() with Err on unknown JWK type

MEDIUM:

• GAPTOS-013: add tracing::warn! for network address parsing fallback

LOW:

• GAPTOS-015: fix ChainId FromStr to parse as u64 instead of u8
• GAPTOS-017: include g_ext in SignedTransaction PartialEq
• GAPTOS-020: replace eprintln!() with tracing::error!()

INFO:

• GAPTOS-INFO-001: translate Chinese comments to English in consensus_config.rs
• GAPTOS-INFO-005: change impl Into to impl From for GravityEvent