fix(ci): Discord notification image URLs to use raw GitHub content

Replace GitHub blob URLs with raw.githubusercontent.com URLs to ensure
Discord embeds can properly display images. Blob URLs serve HTML pages
rather than direct image content, which Discord webhooks cannot render.

Changes:
- prerelease-discord-notification.yml: Update image and avatar_url
- release-discord-notification.yml: Update image and avatar_url

Both workflows now use raw.githubusercontent.com URLs that return direct
image data with proper MIME types for Discord embed rendering.

Author: LittleCoinCoin

.github/workflows/prerelease-discord-notification.yml

@@ -26,5 +26,5 @@ jobs:
             Help us make *Hatch!* better by testing and reporting [issues](https://github.com/CrackingShells/Hatch/issues)! 🐛➡️✨
           color: 0xff9500  # Orange color for pre-release
           username: "Cracking Shells Pre-release Bot"
-          image: "https://github.com/CrackingShells/.github/blob/main/resources/images/hatch_icon_dark_bg_transparent.png"
-          avatar_url: "https://github.com/CrackingShells/.github/blob/main/resources/images/cs_core_dark_bg.png"
+          image: "https://raw.githubusercontent.com/CrackingShells/.github/main/resources/images/hatch_icon_dark_bg_transparent.png"
+          avatar_url: "https://raw.githubusercontent.com/CrackingShells/.github/main/resources/images/cs_core_dark_bg.png"

.github/workflows/release-discord-notification.yml

@@ -25,5 +25,5 @@ jobs:
             Happy MCP coding with *Hatch!* 🐣
           color: 0x00ff88
           username: "Cracking Shells Release Bot"
-          image: "https://github.com/CrackingShells/.github/blob/main/resources/images/hatch_icon_dark_bg_transparent.png"
-          avatar_url: "https://github.com/CrackingShells/.github/blob/main/resources/images/cs_core_dark_bg.png"
+          image: "https://raw.githubusercontent.com/CrackingShells/.github/main/resources/images/hatch_icon_dark_bg_transparent.png"
+          avatar_url: "https://raw.githubusercontent.com/CrackingShells/.github/main/resources/images/cs_core_dark_bg.png"