feat(ui): revamp line patch dialog and add merge progress notice

Revamp the line patch dialog to improve usability and clarity.
Improve accessibility and German/English localization for UI text.
Add toolbar, hunk navigation, per-line checkbox selection and footer.
Extract merge-in-progress UI into a reusable merge progress notice.

- Replace selection UI with checkboxes, range selection, and counts
- Add hunk navigation, active-hunk tracking, and scroll synchronization
- Extract merge-in-progress UI into a reusable notice component

src/App.svelte

@@ -29,6 +29,7 @@
   import ExplorerPanel from "./lib/components/ExplorerPanel.svelte";
   import HistoryPanel from "./lib/components/HistoryPanel.svelte";
   import InitRepositoryDialog from "./lib/components/InitRepositoryDialog.svelte";
+  import MergeProgressNotice from "./lib/components/MergeProgressNotice.svelte";
   import MergeBranchDialog from "./lib/components/MergeBranchDialog.svelte";
   import NewBranchDialog from "./lib/components/NewBranchDialog.svelte";
   import RenameBranchDialog from "./lib/components/RenameBranchDialog.svelte";
@@ -5500,13 +5501,7 @@
     {/if}
 
     {#if workspaceActive && mergeInProgress}
-      <section class="notice conflict" role="status">
-        <GitMerge size={17} aria-hidden="true" />
-        <span>{hasConflicts ? "Merge in progress. Resolve all conflicts, then continue." : "Merge is ready to be completed."}</span>
-        {#if hasConflicts}<button type="button" onclick={openResolveDialog} disabled={isBusy}>Resolve conflicts</button>{/if}
-        <button type="button" onclick={continueMerge} disabled={isBusy || hasConflicts}>Continue</button>
-        <button type="button" onclick={abortMerge} disabled={isBusy}>Abort</button>
-      </section>
+      <MergeProgressNotice conflictCount={conflictedFiles.length} {isBusy} language={appLanguage} onResolve={openResolveDialog} onContinue={continueMerge} onAbort={abortMerge} />
     {:else if workspaceActive && hasConflicts && !rebaseInProgress && !cherryPickInProgress}
       <section class="notice conflict" role="alert">
         <GitMerge size={17} aria-hidden="true" />