chore(webview): document and pin the Discover bridge v3 contract [PERA-4672]

[yasin-ce]

Description

• Turns the RN <-> web bridge method set into a single enforced source of truth. bridge-methods.ts holds the v3 list plus an isSupportedBridgeMethod guard; usePeraWebviewInterface now rejects anything outside it instead of falling through a switch default.
• Records the contract in docs/DISCOVER_BRIDGE_CONTRACT.md, with a contract test that fails if the list and the dispatch drift apart.
• Adds a webview_bridge_method_not_found analytics event so a page calling outside the contract is visible rather than silently ignored.

Related Issues

• closes https://algorandfoundation.atlassian.net/browse/PERA-4672

Checklist

• Have you tested your changes locally?
• Have you reviewed the code for any potential issues?
• Have you documented any necessary changes in the project's documentation?
• Have you added any necessary tests for your changes?
• Have you updated any relevant dependencies?

Additional Notes

The telemetry is here rather than in a follow-up because the guard needs somewhere to report to — a method that fails closed silently is indistinguishable from a broken bridge when a partner page misbehaves.

The contract test is the part worth keeping honest: it asserts the documented list and the dispatch agree, so adding a method without updating the doc fails CI rather than quietly widening the surface.

[filipetamota]

@yasin-ce QA and code review done ✅