feat(compare): localize compare dialog and refine styles

Add German labels to compare select options and refine styles.
Group names and the current marker are localized for German.
Style tweaks adjust spacing, weights, and muted colors for better
readability and visual consistency.

- Localize option groups and current marker to German.
- Refine dialog typography, spacing, and muted color tokens.

src/lib/components/CompareSelectDialog.svelte

@@ -47,9 +47,21 @@
   let remoteBranches = $derived(branches.filter((branch) => branch.remote));
   let targetCount = $derived(branches.length + commits.length);
   let compareOptions = $derived([
-    ...localBranches.map((branch) => ({ value: branchValue(branch), label: `${branch.name}${branch.current ? " (current)" : ""}`, group: "Branches - Local" })),
-    ...remoteBranches.map((branch) => ({ value: branchValue(branch), label: branch.name, group: "Branches - Remote" })),
-    ...commits.map((item) => ({ value: item.hash, label: commitOptionLabel(item), group: "Commits" })),
+    ...localBranches.map((branch) => ({
+      value: branchValue(branch),
+      label: `${branch.name}${branch.current ? (isGerman ? " (aktuell)" : " (current)") : ""}`,
+      group: isGerman ? "Lokale Branches" : "Local branches",
+    })),
+    ...remoteBranches.map((branch) => ({
+      value: branchValue(branch),
+      label: branch.name,
+      group: isGerman ? "Remote-Branches" : "Remote branches",
+    })),
+    ...commits.map((item) => ({
+      value: item.hash,
+      label: commitOptionLabel(item),
+      group: "Commits",
+    })),
   ]);
 
   function handleSubmit(event: SubmitEvent) {