feat: add dedicated 402 budget limit error page

[HarshMN2345]

Replace generic error display for 402 responses with a dedicated budget limit error page. Includes a 'Go to billing' CTA when an organization is in context, and a 'Change organization' secondary action on both console-level and project-level error pages.

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[greptile-apps]

Greptile Summary

This PR replaces the generic error display for HTTP 402 responses with a dedicated "billing limit reached" page in both the console-level and project-level error boundaries. Each page shows a styled badge, an error message, a conditional "Go to billing" CTA, and a "Change organization" fallback button.

• (console)/+error.svelte — migrated to Svelte 5 runes; derives billingUrl from page.params.organization, so the billing CTA is absent when the error occurs outside an organization-scoped route (intentional, no org = no known billing target).
• (console)/project-[region]-[project]/+error.svelte — adds a 402 branch ahead of the existing general_resource_blocked branch; billingUrl is resolved from the $organization store. Still uses Svelte 4 $: reactive syntax (pre-existing in this file, flagged in an earlier review thread).

Confidence Score: 5/5

Safe to merge — the changes are additive UI-only modifications to error boundary pages with no shared state mutations or breaking contract changes.

Both error pages add a straightforward conditional branch for 402 responses. The billing URL derivation logic is simple and fails safely (null → no button rendered). The console-level file correctly uses Svelte 5 runes; the project-level file's legacy syntax is a pre-existing concern already raised in a prior review thread. No data-layer or auth-path changes are present.

No files require special attention.

Important Files Changed

Filename	Overview
src/routes/(console)/+error.svelte	Adds a dedicated 402 billing-limit error layout using Svelte 5 runes ($derived); billing URL is derived from page.params.organization, correctly resolving to null when no org is in the route context.
src/routes/(console)/project-[region]-[project]/+error.svelte	Adds a 402 branch before the existing general_resource_blocked branch; billing URL is resolved from the $organization store. Still uses legacy $: reactive declarations (noted in a prior thread). Logic is otherwise correct.

_{Reviews (2): Last reviewed commit: "fix: use backend error message on 402 bi..." | Re-trigger Greptile}

[greptile-apps]

Svelte 4 reactive declarations on a touched file

The three new reactive statements use legacy $: syntax (Svelte 4), but AGENTS.md requires migrating a file to Svelte 5 runes when it is modified ("When touching a file, migrate it to runes if practical. Don't mix syntaxes within a single component."). The sibling (console)/+error.svelte was already in runes mode and uses $derived for the equivalent variables; keeping this file on $: means the two error pages diverge in style unnecessarily. The existing $: statements for allOrgsHavePremiumSupport and hasPremiumSupport should also be converted as part of the same pass.

Context Used: AGENTS.md (source)

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