Add 81 x402 ecosystem repositories

[smartflowproai-lang]

Follow-up to the discussion in #2925: @yizhao-ec asked which x402 repos are missing from the taxonomy. This migration adds 81 repositories to the existing x402 ecosystem.

How the list was built:

• swept GitHub for x402-related repositories and cross-checked every candidate against all existing migrations (including repos already tracked under Base, Solana, Ethereum and others), so this only contains repos not currently tracked anywhere in the taxonomy
• filtered for substance: x402 has to be core to the repo (README and topics verified), not a passing mention; forks, archived repos, clones of already-tracked repos and keyword-stuffed listings were dropped
• all 81 URLs verified live before submission

Notable inclusions:

• corporate/official: aws-samples (CloudFront x402 content monetization sample), quiknode-labs, thirdweb-dev + thirdweb-example, NethermindEth (x402-starknet), edgeandnode (ampersend-sdk), veniceai, oasisprotocol, bosonprotocol (x402 escrow reference), apify (mcpc)
• facilitators and chain bindings: project-r0x (Robinhood Chain), nero-x402 (NERO), mogami-tech/x402-facilitator, raid-guild/x402-facilitator-go, elldeeone/kaspa-x402
• SDKs and middleware across languages: TypeScript, Python, Go, Elixir (cardotrejos/x402), SvelteKit, Flask
• security tooling: presidio-hardened-x402, paysentry, mythos-sentinel, red-team-blue-team-agent-fabric
• curated resource lists: xpaysh/awesome-x402, Daehan-Base/awesome-x402-on-base (Korean), Custena/agent-payment-protocols

Happy to keep contributing here as the catalogue grows.