feat: implement comic/manga metadata display on book detail page

Implement comprehensive comic metadata display features on the SSR book detail
page, supporting all 8 metadata fields from ComicInfo.xml and other sources.

## Template Changes (book_detail.templ)

### Step 1: Reading Direction Badge
- Display directional badge (RTL, LTR, VERTICAL) for manga/comics
- Uses 📖 icon with uppercase direction text
- Auto-hides when direction is "auto" (default)
- Styled with accent color for visibility

### Step 2: Community Rating Display
- Show pre-existing community rating from metadata (0.0-10.0 scale)
- Distinct from user ratings with visual differentiation
- Uses renderStars() helper for visual star display
- Shows both stars and numeric score (e.g., "★★★★☆ 8.5 / 10")
- Smaller, subtler styling than user rating

### Step 3: Comic-Specific Badges
- Age Rating: Content maturity indicator
- Black & White: Visual style badge
- Story Arc: Narrative arc name with 📚 icon
- Badges styled as pills with subtle borders
- Only display when values are present

### Step 4: Universal Series Info
- Series Count: Total items in series
- Volume: Volume/omnibus number
- Imprint: Publisher imprint (e.g., Vertigo)

### Step 5: Comic-Specific Metadata
- Manga Type: Raw/Comic/Manga classification
- Scan Information: Scanner group, resolution
- Alternate Series: Different series numbering

### Step 6: Summary Section
- Display ComicInfo.xml summary when present
- Separate from description field
- Sanitized HTML output with bluemonday
- Scrollable container for long summaries

### Step 7: Metadata Notes
- Technical notes from metadata files
- Internal/useful information (scanner, source, etc.)
- Card-style display with clear typography

### Step 8: Web URL Link
- External link to info sources (Goodreads, ComicVine, etc.)
- Opens in new tab with security attributes
- Displays clean domain name

## Utils Changes (templates/utils.go)

Added helper functions:
- getAlternateSeries(): Extract alternate series from JSONB
- getDomainName(): Extract clean domain for display
- formatAlternateInfo(): Format readable alternate series string

## Implementation Plan

Updated FRONTEND_IMPLEMENTATION_PLAN_COMIC_METADATA.md with:
- Disabled markdownlint for MD013 (line length)
- Added spacing for readability

## Technical Details

- All fields use pgtype.Text/Int4/Bool for NULL handling
- Template conditionals check Valid flag before accessing values
- Consistent styling using CSS custom properties
- HTML escaping for security (except summary with bluemonday)
- Responsive design with mobile-friendly layouts

Related: Database schema already supports all metadata fields

templates/utils.go

@@ -2,7 +2,9 @@ package templates
 
 import (
 	"bookhoard/internal/database"
+	"encoding/json"
 	"fmt"
+	"net/url"
 	"strings"
 
 	"github.com/google/uuid"
@@ -142,3 +144,56 @@ func getBookRating(rating *database.MediaRatings) int32 {
 	}
 	return 0
 }
+
+// getAlternateSeries extracts the alternate series name from JSONB data
+func getAlternateSeries(data []byte) string {
+	if len(data) == 0 {
+		return ""
+	}
+	var result map[string]interface{}
+	if err := json.Unmarshal(data, &result); err != nil {
+		return ""
+	}
+	if series, ok := result["alternate_series"].(string); ok {
+		return series
+	}
+	return ""
+}
+
+// getDomainName extracts a clean domain name from URL for display
+func getDomainName(rawURL string) string {
+	if rawURL == "" {
+		return "Source"
+	}
+	u, err := url.Parse(rawURL)
+	if err != nil {
+		return "Source"
+	}
+	// Return hostname without www.
+	hostname := u.Hostname()
+	return strings.TrimPrefix(hostname, "www.")
+}
+
+// formatAlternateInfo formats alternate series info as readable string
+func formatAlternateInfo(data []byte) string {
+	if len(data) == 0 {
+		return ""
+	}
+	var result map[string]interface{}
+	if err := json.Unmarshal(data, &result); err != nil {
+		return ""
+	}
+
+	var parts []string
+	if series, ok := result["alternate_series"].(string); ok && series != "" {
+		parts = append(parts, series)
+	}
+	if num, ok := result["alternate_number"].(float64); ok && num > 0 {
+		parts = append(parts, fmt.Sprintf("#%d", int(num)))
+	}
+	if count, ok := result["alternate_count"].(float64); ok && count > 0 {
+		parts = append(parts, fmt.Sprintf("(of %d)", int(count)))
+	}
+
+	return strings.Join(parts, " ")
+}