Fix sending user_enabled instead of enabled when creating/updating integrations

[Desvelao]

Description

The Content Manager is changing how an integration's enabled state is stored: an integration now carries three boolean fields (cti_enabled, user_enabled, enabled), each written by exactly one actor. Reading keeps using document.enabled unchanged, but the Content Manager now derives enabled itself and rejects create/update requests that still send it directly (400 Missing [user_enabled] field).

This PR renames the field sent in the outgoing create/update payload from enabled to user_enabled, in every space (standard, draft, test, custom).

Closes #427

Proposed Changes

• Added IntegrationResourcePayload type (types/Integrations.ts): the Content Manager resource shape, IntegrationBase['document'] minus enabled plus user_enabled.
• Added toIntegrationResourcePayload() (server/utils/helpers.ts): renames enabled → user_enabled on the document before it is sent to the Content Manager.
• server/services/IntegrationService.ts: createIntegration and updateIntegration now build the outgoing resource body through toIntegrationResourcePayload().
• No changes to read paths (searchIntegrations, PoliciesService, browser code) — they keep using document.enabled as returned by the Content Manager, unchanged.

Results and Evidence

Not yet verified end-to-end: the Content Manager's user_enabled/cti_enabled support depends on the indexer package from wazuh/wazuh-indexer-plugins#1403, which is not yet available. This PR stays in draft until that package is published and the create/update flows can be validated against a real cluster, in every space.

Tests Introduced

• server/utils/helpers.test.ts: unit tests for toIntegrationResourcePayload, covering enabled: true/false and confirming the rest of the document is left untouched across standard/draft/test/custom spaces.

Review Checklist

• Code changes reviewed
• Relevant evidence provided (pending indexer package availability, see above)
• Tests cover the new functionality
• Configuration changes documented (n/a)
• Developer documentation reflects the changes (n/a)
• Meets requirements and/or definition of done (pending validation against the new indexer package)
• No unresolved dependencies with other issues (tracked: wazuh-indexer-plugins#1403)
• PR is linked to the relevant issue(s)
• Correct labels applied (e.g., no-changelog)