feat(dashboard): add link with phone number pairing code UI

[akash247777]

Description

This pull request adds the frontend dashboard UI for the "Link with Phone Number" pairing code feature.

While the NestJS backend API endpoint (POST /api/sessions/:id/pairing-code) was already implemented, there was no way to request or view the pairing code from the dashboard interface.

Key Changes

1. Interactive Toggle Tabs: Modified the session connection modal on the Sessions page to render a toggle switch between the standard "QR Code" scanning mode and the new "Link with Phone Number" mode.
2. Phone Number Input & Validation: Added a phone input field that automatically sanitizes inputs (enforces digits-only) and triggers the pairing code request.
3. Pairing Code Display: Renders the 8-character pairing code in a large, spaced, monospace format (e.g., ABCD - 1234) for high readability.
4. Step-by-step Instructions: Included clear localization-supported instructions in the modal explaining how to link the device on the WhatsApp mobile app.
5. Clean State Management: Integrated state cleanup on modal close (resets phone number, generated codes, and errors).

Type of Change

• New feature

Checklist

• Tests added/updated
• Documentation updated
• Lint passes
• Self-reviewed

Screenshots

[rmyndharis]

Thanks for this, @akash247777 — really nice contribution. The pairing-code endpoint has existed on the backend for a while with no way to reach it from the dashboard, so this fills a genuine gap, and the QR ⇄ phone tab flow reads well.

I've pushed one follow-up commit on top to get it merge-ready against our CI gates and a few UX details:

Required for CI

• Locale parity (npm run i18n:check blocks the build): the new sessions.pairing.* keys were only in en.json, so the other 9 locales failed parity. Added native translations of the full block across ar, es, fr, he, it, pt-BR, te, zh-CN, zh-HK.
• CSS scope guard (styles.scope.test.ts): the new .pairing-* selectors were global; scoped them all under .sessions-page to match the rest of the file and avoid cross-route style bleed.

Correctness / UX

• The "waiting to connect" line referenced sessions.pairing.waitingConnection, which didn't exist in any locale (it rendered the raw key) — added it.
• Invalid-phone validation reused the session-name error ("only lowercase letters… hyphens"); added a phone-specific invalidPhone message.
• Reset the pairing sub-state whenever the modal (re)opens, so opening it for a different session can't show a stale code/number.

Accessibility / polish

• <label htmlFor>/id association, type="tel" + inputMode="numeric" + maxLength, Generate disabled until the number is valid, role="tab"/tabpanel, and the error banner moved to a theme-aware class (the hardcoded #FEE2E2/#DC2626 was unreadable in dark mode).

Full gate is green locally (build, unit tests, eslint, prettier, i18n parity, scope guard); CI is running now. Merging once it's green. Thanks again!