fix(cover): improve readability and brightness based on test print feedback

- Strengthen front overlay tint so subtitle and author text read clearly
  against the artwork (was 20% centre tint, now 30%; bottom band 40%→60%)
- Set front subtitle to white and front author to gold2, both with
  triple-layer text-shadow for maximum contrast
- Increase back content padding from 0.125 in to 0.25 in on all trim edges
- Change back tagline colour from 50%-opacity gold to full --color-text
  with solid black shadow so the quote is legible
- Raise back artwork opacity 0.35→0.55 and reduce overlay darkness so
  the back image is no longer too dark

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

templates/cover.html

@@ -138,11 +138,10 @@
     /* ── Back cover content ─────────────────────────────────── */
     .back-content {
       position: absolute;
-      /* safe zone: bleed + safe from left, safe from right, bleed+safe from top/bottom */
+      top:    calc(var(--bleed) + 0.25in);
-      top:    calc(var(--bleed) + var(--safe));
+      left:   calc(var(--bleed) + 0.25in);
-      left:   calc(var(--bleed) + var(--safe));
+      right:  0.25in;
-      right:  var(--safe);
+      bottom: calc(var(--bleed) + 0.25in);
-      bottom: calc(var(--bleed) + var(--safe));
       display: flex;
       flex-direction: column;
       justify-content: space-between;
@@ -205,10 +204,10 @@
       font-style: italic;
       font-weight: 300;
       font-size: 0.118in;
-      color: var(--color-muted);
+      color: var(--color-text);
       max-width: 60%;
       line-height: 1.6;
-      text-shadow: 0 1px 4px rgba(0,0,0,0.8);
+      text-shadow: 0 1px 6px rgba(0,0,0,1), 0 2px 16px rgba(0,0,0,1);
     }
 
 
@@ -219,7 +218,7 @@
       width: 100%;
       height: 100%;
       object-fit: cover;
-      opacity: 0.35;
+      opacity: 0.55;
     }
 
     /* Gradient vignette — mirrors front-overlay for depth and legibility */
@@ -231,12 +230,12 @@
       background:
         radial-gradient(ellipse 90% 90% at 50% 50%,
           transparent 30%,
-          rgba(6, 6, 24, 0.55) 100%),
+          rgba(6, 6, 24, 0.45) 100%),
         linear-gradient(to bottom,
-          rgba(6, 6, 24, 0.40) 0%,
+          rgba(6, 6, 24, 0.30) 0%,
-          rgba(6, 6, 24, 0.15) 35%,
+          rgba(6, 6, 24, 0.10) 35%,
-          rgba(6, 6, 24, 0.15) 65%,
+          rgba(6, 6, 24, 0.10) 65%,
-          rgba(6, 6, 24, 0.50) 100%);
+          rgba(6, 6, 24, 0.35) 100%);
     }
 
     /* ── Spine content ──────────────────────────────────────── */
@@ -307,14 +306,14 @@
       background:
         /* deep vignette around all edges */
         radial-gradient(ellipse 90% 90% at 50% 50%,
-          transparent 30%,
+          transparent 20%,
-          rgba(6, 6, 24, 0.55) 100%),
+          rgba(6, 6, 24, 0.65) 100%),
-        /* uniform dark tint to lift text off the image */
+        /* stronger tint in the text bands (top + bottom) */
         linear-gradient(to bottom,
-          rgba(6, 6, 24, 0.35) 0%,
+          rgba(6, 6, 24, 0.50) 0%,
-          rgba(6, 6, 24, 0.20) 40%,
+          rgba(6, 6, 24, 0.30) 35%,
-          rgba(6, 6, 24, 0.20) 60%,
+          rgba(6, 6, 24, 0.30) 55%,
-          rgba(6, 6, 24, 0.40) 100%);
+          rgba(6, 6, 24, 0.60) 100%);
     }
 
     .front-content {
@@ -363,8 +362,8 @@
       font-weight: 300;
       font-size: 0.17in;
       letter-spacing: 0.1em;
-      color: rgba(232, 228, 216, 0.92);
+      color: #ffffff;
-      text-shadow: 0 1px 6px rgba(0,0,0,1), 0 2px 16px rgba(0,0,0,0.8);
+      text-shadow: 0 1px 8px rgba(0,0,0,1), 0 2px 24px rgba(0,0,0,1), 0 0 0.3in rgba(0,0,0,0.9);
     }
 
     /* Placeholder box shown when no front artwork is provided */
@@ -396,8 +395,8 @@
       font-weight: 300;
       font-size: 0.15in;
       letter-spacing: 0.12em;
-      color: rgba(184,154,78,0.85);
+      color: var(--color-gold2);
-      text-shadow: 0 1px 6px rgba(0,0,0,1), 0 2px 16px rgba(0,0,0,0.8);
+      text-shadow: 0 1px 8px rgba(0,0,0,1), 0 2px 24px rgba(0,0,0,1), 0 0 0.3in rgba(0,0,0,0.9);
     }
 
     .front-ornament {