fix(markdown): formatting inside bold/italic/strike, monochrome inline code

Bold, italic and strikethrough render their inside again, so **`code`**
shows bold code instead of backticks; inline code uses the theme's code
background with the main text colour instead of the accent colour.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

frontend/src/lib/markdown.tsx

@@ -86,7 +86,7 @@ function renderInlineTokens(text: string, options?: InlineMarkdownOptions): Reac
       }
     } else if (token.startsWith('`') && token.endsWith('`')) {
       elements.push(
-        <code key={key} className="px-1.5 py-0.5 rounded bg-panel-elevated text-accent font-mono text-[0.9em] border border-border/50">
+        <code key={key} className="px-1.5 py-0.5 rounded bg-code text-main font-mono text-[0.9em] border border-border/50">
           {token.slice(1, -1)}
         </code>
       );
@@ -96,7 +96,7 @@ function renderInlineTokens(text: string, options?: InlineMarkdownOptions): Reac
     ) {
       elements.push(
         <strong key={key} className="font-semibold text-main">
-          {token.slice(2, -2)}
+          {renderInlineTokens(token.slice(2, -2), options)}
         </strong>
       );
     } else if (
@@ -105,13 +105,13 @@ function renderInlineTokens(text: string, options?: InlineMarkdownOptions): Reac
     ) {
       elements.push(
         <em key={key} className="italic text-main/90">
-          {token.slice(1, -1)}
+          {renderInlineTokens(token.slice(1, -1), options)}
         </em>
       );
     } else if (token.startsWith('~~') && token.endsWith('~~')) {
       elements.push(
         <del key={key} className="line-through text-muted/80">
-          {token.slice(2, -2)}
+          {renderInlineTokens(token.slice(2, -2), options)}
         </del>
       );
     } else if (token.startsWith('[') && match[2] && match[3] && safeHref(match[3])) {