feat(i18n): translate the whole interface

Mark every UI string the unmarked-text check reported (534) plus text it
cannot see (helpers, joined labels, runtime-built panels), and translate
the result to Spanish and Russian: 1,679 messages each.

- Kept on purpose, with the reason where the text lives: provider and
  product names, place and camera names, codes and units, dB values, the HUD
  terminal readouts, demo shot titles that saved projects look up by title,
  and text for AI tools and the voice model.
- Modules shared with the server or AI tools stay free of the i18n import
  (local msg); the wind reading and voice session stay English and are
  translated where the page shows them.
- npm test now runs the unmarked-text check.
- Fixes on the way: a duplicated radio privacy paragraph, the contact panel
  toggle saying Expand while open, the CSS filter mistaking & for CSS.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

src/ui/templates/welcome.html

@@ -12,7 +12,7 @@
          — including the unspaced em dash. The arc it has to carry: this looks
          like something you should not have access to → the sources are all
          public → the data is real. Tile subcopy stays purely functional. -->
-    <p id="first-run-description">It feels like a forbidden cockpit—then you realize the sources are public and the data is real.</p>
+    <p id="first-run-description" data-i18n-runtime>It feels like a forbidden cockpit—then you realize the sources are public and the data is real.</p>
     <div class="first-run-choices">
       <button type="button" data-first-run-choice="contacts">
         <span class="material-symbols-outlined" aria-hidden="true">radar</span>
@@ -30,7 +30,7 @@
         <!-- Subcopy names BOTH feeds this tile turns on, because the launcher
              optimizes for the fully configured experience (owner ruling,
              2026-08-23) — see the mission table in src/firstRunExperience.js. -->
-        <span><strong data-first-run-environmental-title>ENVIRONMENTAL</strong><small>Live earthquakes and active fires, from USGS and NASA</small></span>
+        <span data-i18n-runtime><strong data-first-run-environmental-title>ENVIRONMENTAL</strong><small>Live earthquakes and active fires, from USGS and NASA</small></span>
         <span class="material-symbols-outlined first-run-arrow" aria-hidden="true">arrow_forward</span>
       </button>
       <button type="button" class="first-run-explore" data-first-run-choice="explore">