feat(theme): add Vesper theme (@SameerJS6) (#6443)

### Description
Adds Vesper theme. Based on Vesper for VSCode theme from [Rauno
Freiberg](https://github.com/raunofreiberg/vesper)

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### Checks

- [ ] Adding quotes?
- [ ] Make sure to include translations for the quotes in the
description (or another comment) so we can verify their content.
- [x] Adding a language or a theme?
- [ ] If is a language, did you edit `_list.json`, `_groups.json` and
add `languages.json`?
  - [x] If is a theme, did you add the theme.css?
- Also please add a screenshot of the theme, it would be extra awesome
if you do so!
- [x] Check if any open issues are related to this PR; if so, be sure to
tag them below.
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parentheses at the end of the PR title.

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## Preview

### Main Page:

![vesper-monkey-type](https://github.com/user-attachments/assets/4d1f7ac0-b139-42e9-b588-e3e9edeae809)

### Settings Page:
![vesper monkey type
settings](https://github.com/user-attachments/assets/274a7551-5555-483e-85c3-efd47797edac)

### Toasts:
#### Error Toast:


![image](https://github.com/user-attachments/assets/8cdc4d20-08b7-4c82-94aa-a3ee55fd779e)

#### Info Toast:


![image](https://github.com/user-attachments/assets/0b40e90d-cd23-4248-b39a-ad3340e46d32)

#### Success Toast:


![image](https://github.com/user-attachments/assets/405d010f-e790-4a32-97d2-2a051b85ec0e)


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frontend/static/themes/_list.json

@@ -55,6 +55,13 @@
     "subColor": "#616161",
     "textColor": "#f5e6c8"
   },
+  {
+    "name": "vesper",
+    "bgColor": "#101010",
+    "mainColor": "#ffc799",
+    "subColor": "#99ffe4",
+    "textColor": "#ffffff"
+  },
   {
     "name": "our_theme",
     "bgColor": "#ce1226",

frontend/static/themes/vesper.css

@@ -0,0 +1,53 @@
+:root {
+  --bg-color: #101010;
+  --main-color: #ffc799;
+  --caret-color: #99ffe4;
+  --sub-color: #a0a0a0;
+  --sub-alt-color: #1c1c1c;
+  --text-color: #ffffff;
+  --error-color: #ff8080;
+  --error-extra-color: #b25959;
+  --colorful-error-color: #99ffe4;
+  --colorful-error-extra-color: #99ffe4;
+}
+
+/* Background & Text Colors */
+#notificationCenter .notif.bad {
+  --notif-border-color: #b25959;
+  --notif-background-color: #ff8080;
+}
+
+#notificationCenter .notif.good {
+  --notif-border-color: #99ffe4;
+  --notif-background-color: #99ffe4;
+}
+
+#notificationCenter .notif.notice {
+  --notif-border-color: #afdbf5;
+  --notif-background-color: #afdbf5;
+}
+
+/* Hover Styles  */
+#notificationCenter .notif:hover.good {
+  --notif-background-color: #6bb29f;
+}
+#notificationCenter .notif:hover.bad {
+  --notif-background-color: #8b4444;
+}
+#notificationCenter .notif:hover.notice {
+  --notif-background-color: #5d91ab;
+  /* #7896a8 */
+}
+
+/* Content Colors  */
+#notificationCenter .notif .message {
+  color: var(--bg-color);
+}
+
+#notificationCenter .notif .message .title {
+  color: var(--bg-color);
+}
+
+#notificationCenter .notif .icon {
+  color: var(--bg-color);
+}