fix(t-paliad-137): remove B1 "Skip step" + fix step-back contrast

The B1 decision tree exposed a "Skip this step" affordance on
intermediate non-leaf nodes that broke the narrowing model — clicking
it left the tree in a half-narrowed state with no clear UX intent.
Drop the button entirely; users who don't know an answer should pick
"Anderes / Sonstiges" or switch to B2 (filter mode).

The step-back button (and its sibling .fristen-b1-loosen-link in the
empty-result state) rendered with `color: var(--color-accent)` over a
transparent background — lime green text on cream is unreadable. Move
both to a secondary-button shape: hairline border, muted text, accent
on focus-visible. Both light and dark themes verified.

Touched:
  - frontend/src/client/fristenrechner.ts: drop skip TSX + handler
  - frontend/src/client/i18n.ts: drop "deadlines.pathway.b.tree.skip"
  - frontend/src/i18n-keys.ts: drop the codegen key
  - frontend/src/styles/global.css: split off .fristen-b1-skip selector
    and replace the lime-text rule with a bordered secondary style
    using --color-text-muted / --color-border (themed both ways)

frontend/src/client/fristenrechner.ts

@@ -1934,14 +1934,6 @@ function renderB1Cascade(currentSlug: string) {
     }</div>`;
   }
 
-  // Skip-step affordance on non-leaf intermediate nodes.
-  let skipHtml = "";
-  if (node && !node.is_leaf && childScope.length > 0) {
-    skipHtml = `<button type="button" class="fristen-b1-skip" data-action="skip">
-      ${escHtml(t("deadlines.pathway.b.tree.skip"))}
-    </button>`;
-  }
-
   // Step-back affordance on any non-root state.
   let backHtml = "";
   if (trail.length > 0) {
@@ -1951,7 +1943,7 @@ function renderB1Cascade(currentSlug: string) {
     </button>`;
   }
 
-  cascade.innerHTML = `${breadcrumbHtml}${question}${buttonsHtml}${skipHtml}${backHtml}`;
+  cascade.innerHTML = `${breadcrumbHtml}${question}${buttonsHtml}${backHtml}`;
 
   // Wire button clicks.
   cascade.querySelectorAll<HTMLButtonElement>(".fristen-b1-button, .fristen-b1-crumb, .fristen-b1-step-back").forEach((btn) => {
@@ -1961,14 +1953,6 @@ function renderB1Cascade(currentSlug: string) {
     });
   });
 
-  // Skip-step clicks the deepest path with current slug as the anchor —
-  // it just means "search at this node level without deeper narrowing".
-  cascade.querySelectorAll<HTMLButtonElement>(".fristen-b1-skip").forEach((btn) => {
-    btn.addEventListener("click", () => {
-      runB1Search(currentSlug);
-    });
-  });
-
   runB1Search(currentSlug);
 }
 

frontend/src/client/i18n.ts

@@ -297,7 +297,6 @@ const translations: Record<Lang, Record<string, string>> = {
     "deadlines.pathway.b.tree.step.back": "Schritt zurück",
     "deadlines.pathway.b.tree.empty": "Keine Treffer für diesen Pfad.",
     "deadlines.pathway.b.tree.reset": "Neu starten",
-    "deadlines.pathway.b.tree.skip": "Diesen Schritt überspringen",
     "deadlines.pathway.b.tree.start_question": "Was ist passiert?",
     "deadlines.filter.forum.label": "Gericht / System:",
     "deadlines.filter.forum.upc_cfi": "UPC CFI",
@@ -1881,7 +1880,6 @@ const translations: Record<Lang, Record<string, string>> = {
     "deadlines.pathway.b.tree.step.back": "step back",
     "deadlines.pathway.b.tree.empty": "No matches for this path.",
     "deadlines.pathway.b.tree.reset": "Restart",
-    "deadlines.pathway.b.tree.skip": "Skip this step",
     "deadlines.pathway.b.tree.start_question": "What happened?",
     "deadlines.filter.forum.label": "Forum / System:",
     "deadlines.filter.forum.upc_cfi": "UPC CFI",

frontend/src/i18n-keys.ts

@@ -693,7 +693,6 @@ export type I18nKey =
   | "deadlines.pathway.b.tree.coming_soon"
   | "deadlines.pathway.b.tree.empty"
   | "deadlines.pathway.b.tree.reset"
-  | "deadlines.pathway.b.tree.skip"
   | "deadlines.pathway.b.tree.start_question"
   | "deadlines.pathway.b.tree.step.back"
   | "deadlines.pathway.back"

frontend/src/styles/global.css

@@ -1781,22 +1781,29 @@ input[type="range"]::-moz-range-thumb {
     flex: 1;
 }
 
-.fristen-b1-skip,
 .fristen-b1-step-back,
 .fristen-b1-loosen-link {
     background: none;
-    border: none;
-    color: var(--color-accent);
+    border: 1px solid var(--color-border);
+    border-radius: var(--radius);
+    color: var(--color-text-muted);
     cursor: pointer;
-    padding: 0.25rem 0.5rem;
+    padding: 0.35rem 0.75rem;
     font-size: 0.9rem;
     margin-right: 0.5rem;
+    transition: border-color 0.15s ease, color 0.15s ease;
 }
 
-.fristen-b1-skip:hover,
 .fristen-b1-step-back:hover,
 .fristen-b1-loosen-link:hover {
-    text-decoration: underline;
+    border-color: var(--color-text-muted);
+    color: var(--color-text);
+}
+
+.fristen-b1-step-back:focus-visible,
+.fristen-b1-loosen-link:focus-visible {
+    outline: 2px solid var(--color-accent);
+    outline-offset: 2px;
 }
 
 .fristen-b1-error {