feat(nextcloud): add CalDAV/CardDAV redirects to HTTPRoute

[somaz94]

Description of the change

The chart's HTTPRoute template (route.yaml) always added backendRefs to every rule, which made it impossible to define a rule using a RequestRedirect filter (Gateway API rejects RequestRedirect combined with backendRefs). This PR:

• Only renders backendRefs for rules that do not use a RequestRedirect filter, so redirect rules can now be defined.
• Adds the standard Nextcloud service discovery redirects (/.well-known/carddav and /.well-known/caldav -> /remote.php/dav) as RequestRedirect rules, gated behind httpRoute.wellKnown.enabled (on by default). With Gateway API these need no implementation-specific config.

Benefits

CalDAV/CardDAV service discovery works out of the box for Gateway API users, matching the ingress-nginx server-snippet behaviour already documented in the README.

Possible drawbacks

httpRoute.wellKnown.enabled defaults to true, so users who already enable httpRoute get the two redirect rules added on upgrade. Set httpRoute.wellKnown.enabled: false to opt out.

Applicable issues

• fixes Feature: HTTPRoute Add caldav and webdav redirect rules #860

Additional information

Validated locally with helm lint and helm template for: default (redirects + catch-all), wellKnown.enabled=false, and a user-supplied RequestRedirect rule (confirmed no backendRefs is rendered).

Checklist

• I have read the CONTRIBUTING.md doc.
• DCO has been signed off on the commit.
• Chart version bumped in Chart.yaml according to semver.
• (optional) Parameters are documented in the README.md