feat(frontend): rename route to /korrespondenz, update i18n, regen API types

Moves conversations/ to korrespondenz/, updates all internal links,
renames nav label and page heading to Korrespondenz across de/en/es,
and adds all new i18n keys for the redesigned strip and log.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

frontend/src/routes/AppNav.svelte

@@ -60,9 +60,9 @@ function handleOverlayKeydown(event: KeyboardEvent) {
 		</a>
 
 		<a
-			href="/conversations"
+			href="/korrespondenz"
 			class="inline-flex items-center px-3 py-1.5 font-sans text-xs font-bold tracking-widest uppercase transition-colors
-                   {page.url.pathname.startsWith('/conversations')
+                   {page.url.pathname.startsWith('/korrespondenz')
                     ? 'rounded bg-nav-active text-ink'
                     : 'rounded text-ink-2 hover:bg-muted hover:text-ink'}"
 		>
@@ -161,9 +161,9 @@ function handleOverlayKeydown(event: KeyboardEvent) {
 				</a>
 
 				<a
-					href="/conversations"
+					href="/korrespondenz"
 					class="block flex min-h-[44px] w-full items-center px-4 py-3 font-sans text-sm font-bold tracking-widest uppercase transition-colors
-                           {page.url.pathname.startsWith('/conversations')
+                           {page.url.pathname.startsWith('/korrespondenz')
                             ? 'bg-nav-active text-ink'
                             : 'text-ink-2 hover:bg-muted hover:text-ink'}"
 				>