Fix diff viewer contrast issues in modern skins

- Catppuccin: Improved contrast with darker backgrounds for better readability
- Matte-Black: Replaced toxic bright green with muted dark green tones
- Tokyo-Night: Fixed purple-on-purple issue, now uses proper contrast
- Osaka-Jade: Adjusted jade/teal tones to be less bright and more readable
- Ristretto: Toned down bright colors while maintaining coffee theme
- Rose-Pine: Adjusted rose/pine colors for better contrast

All changes maintain theme identity while significantly improving readability
in the diff viewer. Background colors are now more muted and provide better
contrast with foreground text.

Addresses PR review feedback about toxic/poor contrast colors in diff viewer.

Signed-off-by: Rafael Zago <rafaelvzago@gmail.com>

Author: rafaelvzago

misc/skins/catppuccin256.ini

@@ -124,12 +124,12 @@
     viewselected = color228;color189
 
 [diffviewer]
-    added = color189;color151
-    changedline = color69;color189
-    changednew = color210;color189
-    changed = color189;color69
-    removed = color189;color210
-    error = color210;color250
+    added = color234;color108
+    changedline = color189;color24
+    changednew = color210;color24
+    changed = color189;color60
+    removed = color234;color131
+    error = color210;color234
 
 [widget-panel]
     sort-up-char = ↑

misc/skins/matte-black256.ini

@@ -123,12 +123,12 @@
     viewselected = color255;color240
 
 [diffviewer]
-    added = color250;color82
-    changedline = color235;color240
-    changednew = color196;color240
-    changed = color250;color240
-    removed = color250;color196
-    error = color196;color248
+    added = color250;color22
+    changedline = color250;color238
+    changednew = color196;color238
+    changed = color250;color24
+    removed = color250;color52
+    error = color196;color235
 
 [widget-panel]
     sort-up-char = ↑

misc/skins/osaka-jade256.ini

@@ -123,12 +123,12 @@
     viewselected = color120;color66
 
 [diffviewer]
-    added = color188;color119
-    changedline = color22;color66
-    changednew = color167;color66
-    changed = color188;color66
-    removed = color188;color167
-    error = color167;color248
+    added = color234;color29
+    changedline = color188;color23
+    changednew = color167;color23
+    changed = color188;color30
+    removed = color234;color88
+    error = color167;color234
 
 [widget-panel]
     sort-up-char = ↑

misc/skins/ristretto256.ini

@@ -123,12 +123,12 @@
     viewselected = color222;color94
 
 [diffviewer]
-    added = color187;color119
-    changedline = color58;color94
-    changednew = color203;color94
+    added = color234;color58
+    changedline = color187;color52
+    changednew = color203;color52
     changed = color187;color94
-    removed = color187;color203
-    error = color203;color248
+    removed = color234;color88
+    error = color203;color234
 
 [widget-panel]
     sort-up-char = ↑

misc/skins/rose-pine256.ini

@@ -124,12 +124,12 @@
     viewselected = color222;color139
 
 [diffviewer]
-    added = color188;color183
-    changedline = color96;color139
-    changednew = color203;color139
-    changed = color188;color139
-    removed = color188;color203
-    error = color203;color248
+    added = color234;color65
+    changedline = color188;color53
+    changednew = color203;color53
+    changed = color188;color60
+    removed = color234;color88
+    error = color203;color234
 
 [widget-panel]
     sort-up-char = ↑

misc/skins/tokyo-night256.ini

@@ -124,12 +124,12 @@
     viewselected = color221;color69
 
 [diffviewer]
-    added = color147;color148
-    changedline = color255;color69
-    changednew = color203;color69
-    changed = color147;color69
-    removed = color147;color203
-    error = color203;color252
+    added = color234;color108
+    changedline = color147;color17
+    changednew = color203;color17
+    changed = color147;color24
+    removed = color234;color131
+    error = color203;color234
 
 [widget-panel]
     sort-up-char = ↑