fix(x402): stop prefix bypass in service allowlist matching

[SashaMIT]

Description

isServiceRegistered / is_service_registered previously treated a service as allowed when url.startsWith(registered). That enables classic prefix bypasses, for example registering https://api.example.com and later requesting https://api.example.com.evil.com/....

This changes matching to:

• bare origin registration → any path on that origin
• full registered URL → same origin and exact path or segment-boundary path prefix

TypeScript and Python providers are updated together. Adds unit tests for the bypass cases.

AI disclosure

Drafted with AI assistance; reviewed against the allowlist bypass class (hostname-suffix / unsafe prefix matching).

Test plan

• Unit tests for hostname-suffix rejection and valid origin/path cases
• CI on this PR
• Confirm existing registered-origin configs still allow intended paths

[cb-heimdall]

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