feat(ui): error & state UX — error surface, view states, map selection, sheet gestures (F4)

- lib/error/: classify any caught error into a stable ErrorKind from the
  transport signal (HTTP status / Connect Code / fetch TypeError /
  navigator.onLine); map to translated error.* messages via reportError
  (sticky Retry toast for retryable kinds) or errorMessageKey (inline).
  Mail compose now surfaces the translated 403/error inline.
- lib/ui/view-state.svelte: shared loading/empty/error placeholder with
  the right live-region role + optional action; entity tables
  (races/sciences/ship-classes) migrated, rest adopt incrementally.
- map/selection-ring.ts: accent ring around the selected planet, fed into
  the map buildExtras alongside the reach circles.
- lib/ui/sheet-dismiss.ts: tap-outside + drag-handle swipe-down dismissal
  for the planet/ship-group bottom-sheets (hand-rolled pointer events).

Tests: error, view-state, selection-ring, sheet-dismiss (761 total).
Docs: ui/docs/error-state-ux.md (+ index); F4 marked done.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

ui/frontend/src/lib/i18n/locales/en.ts

@@ -9,10 +9,23 @@ const en = {
 	"common.loading": "loading…",
 	"common.dismiss": "dismiss",
 	"common.skip_to_content": "skip to main content",
+	"common.retry": "retry",
 	"common.browser_not_supported_title": "browser not supported",
 	"common.browser_not_supported_body":
 		"Galaxy requires Ed25519 in WebCrypto. See supported browsers.",
 
+	"error.offline":
+		"You appear to be offline. Check your connection and try again.",
+	"error.network": "Couldn't reach the server. Please try again.",
+	"error.auth": "Your session has expired. Please sign in again.",
+	"error.forbidden": "You don't have permission to do that.",
+	"error.conflict":
+		"This changed since you loaded it. Refresh and try again.",
+	"error.not_found": "Not found — it may have been removed.",
+	"error.rate_limit": "Too many requests. Wait a moment and try again.",
+	"error.server": "The server ran into a problem. Please try again.",
+	"error.unknown": "Something went wrong.",
+
 	"game.events.turn_ready.message": "turn {turn} is ready",
 	"game.events.turn_ready.action": "view now",
 	"game.events.signature_failed": "verification failed, reconnecting…",