feat: rename ClawChat → PinchChat across entire project

- Update package.json name and repo URL
- Update README.md, CONTRIBUTING.md branding and links
- Update UI components (Header, Chat) display names
- Update gateway user-agent string
- Rename GitHub repo via API
- Mark FEEDBACK.md item #1 as done

CONTRIBUTING.md

@@ -1,4 +1,4 @@
-# Contributing to ClawChat
+# Contributing to PinchChat
 
 Thanks for your interest in contributing! 🦞
 
@@ -7,8 +7,8 @@ Thanks for your interest in contributing! 🦞
 1. **Fork** the repository
 2. **Clone** your fork:
    ```bash
-   git clone https://github.com/<your-username>/clawchat.git
-   cd clawchat
+   git clone https://github.com/<your-username>/pinchchat.git
+   cd pinchchat
    ```
 3. **Install dependencies:**
    ```bash