Add Stellar-native features to the index

Add Stellar-native features: SEP-8 approval server, claimable balance escrow, clawback safeguard, post-quantum readiness, anchor KYC bridging

Add advanced feature specs: recursive folding, threshold oracle, timelock disclosure, real-time revocation, FHE spending limits, formal verification

Add Reso ZK compliance SaaS scaffold, architecture docs, and brand assets