feat(locale): bootstrap Estonian (et) locale with i18n + 5 news sources

[zionappp-ui]

What this adds

Full Estonian (`et`) locale bootstrap.

Locale changes

• `src/services/i18n.ts` — `'et'` in `SUPPORTED_LANGUAGES` + `LANGUAGES` (`Eesti 🇪🇪`)
• `src/utils/map-locale.ts` — `et: 'name:et'`
• `public/offline.html` — Estonian offline strings
• `scripts/translate-locales.mjs` + `sync-offline-translations.mjs` — `'et'` added
• `src/locales/et.json` — locale bundle with Estonian overlay

Sources (5 feeds, all verified live via direct RSS)

Source	Type	RSS	Items	Tier
ERR (public broadcaster)	mainstream	direct	50	1
Postimees	mainstream	direct	25	1
Delfi ET	mainstream	direct	100	2
EPL (Eesti Päevaleht)	mainstream	direct	50	2
Äripäev	market	direct	25	2

ERR (Eesti Rahvusringhääling) is Estonia's public broadcaster. All 5 feeds use direct RSS — Estonia has unusually good direct feed support.

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[greptile-apps]

Greptile Summary

This PR bootstraps the Estonian (et) locale for WorldMonitor, adding i18n registration, 5 direct-RSS Estonian news sources, offline strings, and an allowlist update across all four domain allowlists (api/, shared/, scripts/shared/, vite.config.ts). The locale uses an overlay approach — only a small set of shell/offline strings are translated to Estonian; all other keys fall back to English via fallbackLng.

• 5 RSS feeds (ERR, Postimees, Delfi ET, EPL, Äripäev) added with consistent entries in both the client (src/config/feeds.ts) and server (server/worldmonitor/news/v1/_feeds.ts), passing the feeds-client-server-parity test requirement.
• shell.metaDescription is explicitly set to English text in et.json rather than being omitted; because i18next only falls back for absent keys, Estonian users will see this in English while other locales (zh, ja, vi, it) have it translated.
• map-locale.test.mts snapshot is not updated to include the new et: 'name:et' tile-field mapping, leaving it untested against future regressions.

Confidence Score: 4/5

Safe to merge; the Estonian locale and news source additions are well-contained and consistent across all required files.

All four RSS domain allowlists, both feed config files, source-tiers, and i18n registration are updated in sync. The feeds-client-server-parity test will pass because both client and server use identical direct-RSS URLs for all five new feeds. The only gaps are a meta description string that should be absent (or translated) in the locale file, and a missing snapshot entry in the map-locale test.

src/locales/et.json (shell.metaDescription left as English text rather than absent) and tests/map-locale.test.mts (new et tile-field mapping not covered by snapshot).

Important Files Changed

Filename	Overview
src/locales/et.json	New 3,269-line Estonian locale bundle added as an overlay; shell titles and a few countryBrief strings are translated to Estonian while most other keys are left in English (relying on i18next fallback). shell.metaDescription is explicitly set in English rather than being absent, unlike zh/ja/vi/it which have it translated.
src/config/feeds.ts	5 Estonian feeds added to FULL_FEEDS europe section and SOURCE_TYPES; all use direct RSS URLs and match server-side entries. Source type classification looks correct (ERR/Postimees/Delfi/EPL as mainstream, Äripäev as market).
server/worldmonitor/news/v1/_feeds.ts	5 Estonian feeds added to VARIANT_FEEDS.full.europe, mirroring client-side entries. Direct RSS URLs match the client. feeds-client-server-parity test should pass.
src/services/i18n.ts	'et' added to SUPPORTED_LANGUAGES (alphabetically placed) and to the LANGUAGES display array with correct label and flag. The locale will be lazy-loaded on demand and falls back to English for missing keys.
src/utils/map-locale.ts	et: 'name:et' mapping added; OSM/Protomaps tiles carry name:et for Estonian place names, so this is correct. The map-locale.test.mts snapshot is not updated to cover the new mapping.
api/_rss-allowed-domains.js	5 Estonian RSS domains added; consistent with vite.config.ts, scripts/shared/rss-allowed-domains.json and shared/rss-allowed-domains.json — all four allowlists updated in sync.
scripts/sync-offline-translations.mjs	'et' added to LOCALES array; 'en' was also reordered from index 0 to its alphabetical position — behaviorally benign since the script iterates without order dependency.
shared/source-tiers.json	5 Estonian sources added with correct tiers (ERR/Postimees at 1, Delfi ET/EPL/Äripäev at 2); non-ASCII characters in pre-existing entries are escaped to Unicode sequences.

Sequence Diagram

sequenceDiagram
    participant Browser
    participant i18n as i18n.ts (initI18n)
    participant Locale as src/locales/et.json
    participant EN as src/locales/en.json (fallback)
    participant FeedConfig as src/config/feeds.ts
    participant RSSProxy as api/_rss-allowed-domains.js
    participant Server as server/_feeds.ts
    participant RSS as Estonian RSS feeds

    Browser->>i18n: detect language (navigator / wm-locale-explicit)
    i18n->>Locale: lazy-load et.json
    Locale-->>i18n: partial bundle (shell + a few countryBrief strings)
    i18n->>EN: addResourceBundle merge (fallbackLng for missing keys)
    EN-->>Browser: rendered UI (Estonian shell titles + English rest)

    Browser->>FeedConfig: resolve FULL_FEEDS.europe
    FeedConfig-->>Browser: ERR, Postimees, Delfi ET, EPL, Äripäev (rssProxyUrl)
    Browser->>RSSProxy: "GET /rss-proxy?url=https://www.err.ee/rss"
    RSSProxy->>RSS: fetch feed (domain allowlist check passed)
    RSS-->>Browser: news items

    Server->>RSS: direct fetch via VARIANT_FEEDS.full.europe (digest path)

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[greptile-apps]

shell.metaDescription left in English

This key is explicitly present in et.json with its English value rather than being absent. Because i18next's fallbackLng: 'en' only fires when a key is missing from the bundle — not when it exists with an English value — Estonian-language users will see this English string instead of a translated version. Other locales (zh, ja, vi, it) all have this translated. Either translate it to Estonian or remove the key so fallback takes effect naturally.