feat(locales): add complete Arabic translation (#174)

## What

Adds a complete Arabic (`ar`) locale covering all 1,850 keys in the
English source catalog.

## Why

Arabic users currently fall back to English throughout Empryo. This
translation provides professional Arabic copy across the shared UI,
Desktop app, and TUI while preserving product names, technical
identifiers, commands, and every runtime placeholder. The Desktop app
can render it with RTL layout support; the terminal retains the bidi
limitation documented in `locales/README.md`.

## Scope check

- [x] I read `CONTRIBUTING.md`; `locales/README.md` explicitly invites
translation PRs.
- [x] This PR changes only `locales/ar.json` and touches no protected
architecture path.
- [x] One focused change: the Arabic locale.
- [x] No application behavior or source code changed; the dedicated
locale gate and its tests pass.

## Verification

- `bun scripts/validate-locales.ts ar` (Bun 1.3.13): `ok ar 100%
translated (1850/1850)`
- `bun test scripts/validate-locales.test.ts` (Bun 1.3.13): 22 passed, 0
failed
- JSON/key audit: 1,850/1,850 keys, source order preserved, 0 unknown, 0
missing
- Placeholder/security audit: 0 placeholder mismatches, 0 forbidden or
bidi-override characters, NFC-normalized
- Product-name audit: no source product names were dropped

Co-authored-by: fares <aw674860@gmail.com>

Author: fares111111122