Billing & Payments page with full i18n

[XK4MiLX]

Summary

This PR introduces the complete Billing & Payments page for FluxOS Frontend, allowing users to track their Flux app payment history with a rich, responsive UI.

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New Features

Billing Page (src/pages/billing/payments.vue)

• Payment history table — lists all apps with total paid, payment count, average payment, and a Details button
• Transaction details dialog — per-app transaction breakdown with type, amount, date, block height and explorer link
• Smart transaction type detection — classifies each fluxappupdate as either Renewal or Update:
  • fluxappregister → Registration
  • spec version < 6 (no expire field) → Renewal
  • spec version ≥ 6: only expire changed or nothing changed → Renewal, otherwise → Update
• Payment trend chart — interactive chart with app filter, view (daily/weekly/monthly), period (7d/30d/90d/1y/all) and metric (amount/count) controls
• Stats cards — total paid, transactions, registrations %, updates %, average cost, highest payment
• Currently running apps section with live instance counts
• Export dialog — export payment history to CSV with date range options (all time, 7/30/90 days, last year, custom range)
• Custom pagination — both main table and transaction dialog use matching custom paginator (first/prev/pages/next/last + showing chip)
• Mobile responsive — category pills wrap with equal widths, icons hidden on small screens, footer label hidden on mobile

Billing Service (src/services/BillingService.js)

• Fetches permanent messages from FluxOS API
• Filters and maps transaction data per address

Router (src/plugins/1.router/guards.js)

• Added billing route guard

Navbar (src/layouts/components/UserProfile.vue)

• Added Billing link to user profile menu

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i18n

Complete billing translation structure added to 22 locale files (en, pl + 20 others):

• New sections: transactionTable, stats, chart (with timeRanges, displayModes, aggregation)
• Updated table structure to match new summary table columns
• Polish grammar corrections (genitive plural forms)
• All 20 non-English locales were missing ~33 keys — now fully in sync with en.json

Languages updated: ar, bn, de, es, fr, hi, id, it, ja, jv, ko, mr, pa, pt, ru, ta, te, tr, vi, zh-CN

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Test plan

• Visit /billing — page loads, payment history fetches correctly
• Click Details on an app row — dialog opens with transaction list and pagination
• Verify transaction types show as Registration / Renewal / Update with correct colors
• Test chart controls: app filter search, view, period, metric selectors
• Export CSV — try all date range options including custom range
• Switch language to PL, DE, FR, RU, ZH — verify all billing strings translate
• Check mobile layout — pills fit on one row, footer label hidden, dialog stats wrap 2×2
• Visit billing then check navbar language/theme switcher — font should be unchanged