fix: silent New Session fallback with toast + v2 path fix + i18n parity

[Probablism]

Summary

Fixes#37606 — "New Session" button silently does nothing when no project is opened.

This is a non-overlapping follow-up to existing PRs #37607 (ndj888) and #38992 (Luppa90), adding:

• Toast feedback when no project is available for New Session
• v2 path query fix for /new endpoint
• Complete i18n parity across all 18 locales
• Info toast variant addition to ToastVariant type union

Changes

File	Change
packages/ui/src/components/toast.tsx	Add "info" to ToastVariant union
packages/app/src/components/titlebar.tsx	Wire toast feedback for New Session
packages/app/src/context/global-sync/bootstrap.ts	Handle missing project gracefully
packages/app/src/context/server-sync.tsx	Remove unused import
packages/app/src/pages/home/home-controller.ts	Show info toast when no project
packages/app/src/pages/home/home-sessions-controller.tsx	Fix v2 path query
packages/app/vite.config.ts	Fix /new endpoint path
packages/app/src/i18n/*.ts (18 locales)	Add toast message translations

Verification

• Typecheck: passes
• Tests: 670/671 pass (1 pre-existing unrelated failure)

[github-actions]

This PR doesn't fully meet our contributing guidelines and PR template.

What needs to be fixed:

• PR description is missing required template sections. Please use the PR template.

Please edit this PR description to address the above within 2 hours, or it will be automatically closed.

If you believe this was flagged incorrectly, please let a maintainer know.

[github-actions]

The following comment was made by an LLM, it may be inaccurate:

Based on the search results, I found one related PR that should be noted:

Related PR:

• fix(app): create fresh web sessions in server directory #37607 - "fix(app): create fresh web sessions in server directory" by ndj888
  • This PR is explicitly mentioned in the current PR description as a non-overlapping follow-up. The current PR (39675) builds upon the work done in fix(app): create fresh web sessions in server directory #37607, adding toast feedback and additional fixes.

The PR description also mentions #38992 by Luppa90 as another related PR in this follow-up chain, though it didn't appear in these search results.

The current PR (39675) is described as a non-overlapping follow-up, meaning it's intentionally complementary rather than duplicative of these earlier PRs.