feat: add event schema compatibility validation

[IgweHub1]

Closes #700

Summary

• Adds a manifest-based event schema compatibility validator for Soroban contract events against the consumer schema.
• Removes duplicate/conflicting contract event declarations so the source schema is canonical.
• Adds checked-in consumer schema baseline and regression tests for valid and invalid payloads.
• Adds CI workflow coverage for the schema compatibility gate.

Verification

listener@1.0.0 test
node ./node_modules/jest/bin/jest.js --runTestsByPath src/schema/compatibility-check.test.ts --runInBand --coverage --collectCoverageFrom=src/schema/compatibility-check.ts

------------------------|---------|----------|---------|---------|------------------------

File	% Stmts	% Branch	% Funcs	% Lines	Uncovered Line #s
All files	70.17	57.64	73.33	73.33
compatibility-check.ts	70.17	57.64	73.33	73.33	90,172,198-202,206-248
------------------------	---------	----------	---------	---------	------------------------

listener@1.0.0 check:event-schema
ts-node src/schema/compatibility-check.ts --format summary

Event Schema Compatibility Check: PASS
Breaking changes: 0

Notes

• Type-checking the entire listener package still fails because of pre-existing unrelated TypeScript syntax issues outside this issue scope.

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