feat: enforce custom domain plan limits in UI

[HarshMN2345]

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[greptile-apps]

Greptile Summary

This PR enforces custom domain plan limits in the UI by adding domains to the PlanServices type, wiring up isServiceLimited checks, and wrapping "Add domain" buttons in Tooltip/disabled states across four pages. It also migrates the org-level domains page to Svelte 5 runes and improves the planComparisonBox to surface domain limits.

• The functions (function-[function]/domains) and sites (site-[site]/domains) pages both pass data.proxyRules.total — scoped to the current resource only — to isServiceLimited, while checkForProjectLimitation classifies domains as a per-project limit. A user can bypass the cap by distributing domains across multiple functions or sites within the same project.

Confidence Score: 4/5

Not safe to merge until the per-resource vs. per-project count mismatch in the functions and sites domain pages is resolved.

One P1 logic defect: both the function and site domain pages pass a per-resource proxy rule count to a per-project limit check, meaning the cap can be silently bypassed by distributing domains across multiple resources. All other changes (billing.ts type extension, planComparisonBox, settings/domains, org/domains rune migration) are clean.

src/routes/(console)/project-[region]-[project]/functions/function-[function]/domains/+page.svelte and src/routes/(console)/project-[region]-[project]/sites/site-[site]/domains/+page.svelte

Important Files Changed

Filename	Overview
src/routes/(console)/project-[region]-[project]/functions/function-[function]/domains/+page.svelte	Adds domain limit enforcement with Tooltip + disabled Button, but uses per-function proxy rule count against a per-project limit, allowing the limit to be bypassed across multiple functions/sites.
src/routes/(console)/project-[region]-[project]/sites/site-[site]/domains/+page.svelte	Same per-resource count vs. per-project limit mismatch as the functions domains page — data.proxyRules.total is scoped to the current site only.
src/routes/(console)/project-[region]-[project]/settings/domains/+page.svelte	Correctly adds domain limit enforcement using project-wide API-type rule count; Svelte 5 runes syntax already in use.
src/routes/(console)/organization-[organization]/domains/+page.svelte	Migrates state declarations to Svelte 5 runes ($props, $state); correctly omits domain limit enforcement at the org level to avoid cross-project scope issues raised in prior review.
src/lib/stores/billing.ts	Adds 'domains' to PlanServices union and checkForProjectLimitation switch — straightforward and correct.
src/lib/components/billing/planComparisonBox.svelte	Adds domain limit/unlimited display to both list styles; logic is internally consistent with the existing pattern.

_{Reviews (2): Last reviewed commit: "fix: greptile comments" | Re-trigger Greptile}