fix: preserve element attributes and styling during markdown injection

Critical fixes:
- Fixed HTML injection to preserve original element attributes, classes, and styling
- Updated markdown processor to generate inline content instead of wrapped paragraphs
- Enhanced content type handling: database type now takes precedence over parser detection
- Eliminated nested <p> tags issue that was causing invalid HTML

Key improvements:
- Elements like <p class='lead insertr' style='color: blue;'> now maintain all attributes
- Markdown **bold**, *italic*, [links](url) inject as inline formatted content
- Database content type (markdown/text/link) overrides parser auto-detection
- Clean HTML output without structural corruption

Before: <p class='lead'><p>**bold**</p></p> (broken)
After:  <p class='lead'>**bold text**</p> (clean)

Server remains source of truth for markdown processing with zero runtime overhead.

internal/content/injector.go

@@ -142,15 +142,16 @@ func (i *Injector) injectLinkContent(node *html.Node, content string) {
 }
 
 // injectHTMLContent safely injects HTML content into a DOM node
+// Preserves the original element and only replaces its content
 func (i *Injector) injectHTMLContent(node *html.Node, htmlContent string) {
-	// Clear existing content
+	// Clear existing content but preserve the element itself
 	i.clearNode(node)
 
 	if htmlContent == "" {
 		return
 	}
 
-	// Wrap content to create valid HTML document for parsing
+	// Wrap content for safe parsing
 	wrappedHTML := "<div>" + htmlContent + "</div>"
 
 	// Parse HTML string
@@ -168,7 +169,7 @@ func (i *Injector) injectHTMLContent(node *html.Node, htmlContent string) {
 		return
 	}
 
-	// Move parsed nodes to target element
+	// Move parsed nodes to target element (preserving original element)
 	for child := wrapper.FirstChild; child != nil; {
 		next := child.NextSibling
 		wrapper.RemoveChild(child)