feat: webhook service frature implemented

[feyishola]

closes #102

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What Was Built

New Files — src/modules/webhooks/

File	Purpose
entities/webhook.entity.ts	TypeORM entity matching the existing migration schema (id, url, secret, events, isActive, lastTriggeredAt)
dto/create-webhook.dto.ts	Validated input DTO for POST /webhooks
dto/webhook-response.dto.ts	Response shape — deliberately excludes the secret field
webhooks.service.ts	Core service: create, findAll, triggerEvent, HMAC signing, delivery with logging
webhooks.controller.ts	GET /webhooks + POST /webhooks, JWT-guarded
webhooks.module.ts	Module that exports WebhooksService for use by other modules
webhooks.service.spec.ts	13 unit tests covering all acceptance criteria

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Modified Files

File	Changes
claim-redemption.provider.ts	Removed all TEMPORARY: markers; restored sweep.completed and sweep.failed triggers
claims.module.ts	Added SweepsModule + WebhooksModule imports (was missing both)
accounts.service.ts	Injected WebhooksService; fires account.created after Stellar account creation succeeds
accounts.module.ts	Added WebhooksModule
scheduler.service.ts	Injected WebhooksService; fires account.expired after marking an account expired
scheduler.module.ts	Added WebhooksModule
app.module.ts	Uncommented ClaimsModule and WebhooksModule
claim-redemption.provider.spec.ts + scheduler.service.spec.ts	Added WebhooksService mocks

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Result

✅ 380 tests pass
✅ Build compiles
✅ Zero TEMPORARY: comments remain

[phertyameen]

Great implementation. Thanks for your contribution.