feat: enhance book detail star rating display with visual half-stars

Improve star rating display on book detail page to show always-visible
5-star rating scale with theme-aware colors and visual half-star rendering.

Changes:

Enhanced renderStars() function:
- Always displays 5 stars (0/5 now shows 5 grey stars instead of empty)
- Filled stars use var(--accent) color (theme-aware highlight)
- Empty stars use var(--text-secondary) (theme-aware grey, adapts to light/dark themes)
- Half-stars use CSS linear-gradient (90deg) to split star vertically:
  - Left half: var(--accent) (filled, color)
  - Right half: var(--text-secondary) (empty, grey)
- Uses webkit-background-clip and text-fill-color transparent for gradient effect

Added getBookRating() helper function:
- Returns rating value or 0 if book.Rating is nil
- Allows unrated books to display 0/5 (5 grey stars)
- Makes rating section always visible instead of hiding when nil

Template changes:
- Updated rating display to always show (no conditionals)
- Removed text-yellow-400 class (colors now inline with theme vars)
- Added templ.Raw() wrapper for HTML rendering (prevents escaping)
- Simplified rating display logic

Benefits:
- Users can now see rating scale even when book isn't rated
- Visual half-star is much more intuitive than ½ text character
- Theme-aware colors adapt to light/dark mode automatically
- Follows existing patterns ( UnsafeHTML, CSS variables, etc.)

This makes the rating section more discoverable and user-friendly.

templates/utils.go

@@ -1,7 +1,9 @@
 package templates
 
 import (
+	"bookhoard/internal/database"
 	"fmt"
+	"strings"
 
 	"github.com/google/uuid"
 	"github.com/jackc/pgx/v5/pgtype"
@@ -36,20 +38,30 @@ func uuidToString(id pgtype.UUID) string {
 }
 
 // renderStars converts rating (1-10 scale) to star display
-// Rating scale: 1-10 where odd numbers = half stars (1=0.5★, 3=1.5★, etc.)
+// Always displays 5 stars total with filled stars in yellow
+// and empty stars in grey (using theme variable)
+// Rating scale: 1-10 where each 2 points = 1 full star, odd numbers = half stars
 func renderStars(rating int32) string {
-	stars := ""
+	const totalStars = 5
 	fullStars := rating / 2
 	hasHalf := rating%2 != 0
 
-	for i := int32(0); i < fullStars; i++ {
-		stars += "★"
-	}
-	if hasHalf {
-		stars += "½"
+	var stars strings.Builder
+
+	for i := int32(0); i < totalStars; i++ {
+		if i < fullStars {
+			// Filled star - accent color (theme-aware highlight)
+			stars.WriteString(`<span style="color: var(--accent);">★</span>`)
+		} else if i == fullStars && hasHalf {
+			// Half star - gradient from accent (left) to grey (right)
+			stars.WriteString(`<span style="background: linear-gradient(90deg, var(--accent) 50%, var(--text-secondary) 50%); -webkit-background-clip: text; -webkit-text-fill-color: transparent;">★</span>`)
+		} else {
+			// Empty star - grey using theme variable
+			stars.WriteString(`<span style="color: var(--text-secondary);">★</span>`)
+		}
 	}
 
-	return stars
+	return stars.String()
 }
 
 // formatFileSize converts bytes to human-readable format
@@ -122,3 +134,11 @@ func getExternalURL(service string, id string, isbn pgtype.Text, title string, a
 
 	return baseURL + searchTerm
 }
+
+// getBookRating returns the rating value or 0 if not rated
+func getBookRating(rating *database.MediaRatings) int32 {
+	if rating != nil {
+		return rating.Rating
+	}
+	return 0
+}