[Web] Translate FeedLocationPickerModal

[mustafa-5493]

📝 [Web] Translate FeedLocationPickerModal

Description

Follow-up to #292. The map-picker modal launched from Feed's "Choose on map" button (frontend/src/components/FeedLocationPickerModal.jsx) was deferred from #534 to keep the main i18n PR's scope tight. Strings still in English include the modal title, the radius indicator, search hints, action buttons (Save / Cancel / Use current location), and the locate-error toast.

Feature / Task Details

• Sweep all user-facing strings in FeedLocationPickerModal.jsx and replace with t() calls.
• Add a feedPicker.* namespace to en.json and tr.json (or extend the existing feed.* block , picker's caller is Feed, so keys naturally fit there).
• Don't translate Nominatim API responses (suggestion display names) , those come from upstream.

Deliverables

• Updated frontend/src/components/FeedLocationPickerModal.jsx
• Updated frontend/src/i18n/locales/en.json and tr.json
• Existing tests should still pass without modification (assertions match the EN strings via i18n fallback)

Acceptance Criteria

• In TR mode, every visible string inside the modal renders in Turkish
• EN mode is identical to before
• Suggestion list still shows Nominatim's raw display_name
• All existing tests pass