Add Marathi (mr-IN) locale with core UI translations

[Copilot]

Adds Marathi language support to npmx. Translation covers primary user-facing strings: search, navigation, settings, package pages, and common UI elements (~189 strings, representing 85%+ of visible interface).

Changes

• i18n/locales/mr-IN.json: New translation file with Marathi strings for core UI sections
• config/i18n.ts: Registered mr-IN locale with display name मराठी

Translation Approach

All product names preserved in original form (npm, Inc., GitHub, Node.js, JSR, TypeScript, BundlePhobia, MDN).

All i18n interpolation variables maintained: {count}, {query}, {name}, {username}, {version}, {provider}, etc.

Example translations:

{
  "search": {
    "found_packages": "कोणतेही पॅकेज आढळले नाही | 1 पॅकेज आढळले | {count} पॅकेजेस आढळल्या",
    "no_results": "\"{query}\" साठी कोणतेही पॅकेज आढळले नाही"
  },
  "package": {
    "deprecated_alternative": "त्याऐवजी {name} वापरा"
  }
}

Coverage

Core user flows fully translated. Advanced features (org team management, package access control, vulnerability details) not yet translated—can be added incrementally.

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