Refactor UI styles to use CSS variables for consistent theming

- Updated background colors across various templates to use CSS variables for better theming support.
- Replaced hardcoded colors with variables like `var(--ui-surface)` and `var(--ui-surface-soft)` for backgrounds.
- Adjusted text colors to use `var(--ui-text)` for improved readability and consistency.
- Enhanced the theme toggle functionality in the base template to dynamically change theme colors based on user preference.
- Ensured that all relevant templates reflect the new theming approach for a cohesive user experience.

Web/templates/reset_item_modal.html

@@ -207,7 +207,7 @@
 }
 
 .reset-item-info {
-    background: #f8f9fa;
+    background: var(--ui-surface-soft);
     border-radius: 8px;
     padding: 20px;
     margin-bottom: 25px;
@@ -216,7 +216,7 @@
 
 .reset-item-info h3 {
     margin: 0 0 15px 0;
-    color: #333;
+    color: var(--ui-text);
     font-size: 1.3rem;
 }
 
@@ -232,7 +232,7 @@
 }
 
 .reset-item-details strong {
-    color: #333;
+    color: var(--ui-text);
 }
 
 .reset-warning-section {
@@ -285,7 +285,7 @@
     flex-direction: column;
     cursor: pointer;
     font-weight: 500;
-    color: #333;
+    color: var(--ui-text);
 }
 
 .reset-action-desc {
@@ -298,7 +298,7 @@
 .active-borrowings {
     margin-top: 10px;
     padding: 10px;
-    background: #f8f9fa;
+    background: var(--ui-surface-soft);
     border-radius: 5px;
     font-size: 0.9rem;
 }
@@ -321,7 +321,7 @@
 
 .reset-options-section h4 {
     margin: 0 0 15px 0;
-    color: #333;
+    color: var(--ui-text);
 }
 
 .reset-option {
@@ -365,7 +365,7 @@
     display: block;
     margin-bottom: 8px;
     font-weight: 500;
-    color: #333;
+    color: var(--ui-text);
 }
 
 .reset-reason-section textarea {
@@ -391,7 +391,7 @@
     display: flex;
     justify-content: flex-end;
     gap: 15px;
-    background: #f8f9fa;
+    background: var(--ui-surface-soft);
     border-radius: 0 0 12px 12px;
 }