feat: add c-token client examples

Add compressed token (cToken) client examples:
- client-create-cmint.rs - Create compressed mint with metadata
- client-create-ctoken.rs - Create compressed token account
- client-create-cata.rs - Create compressed ATA
- client-mint-to-ctoken.rs - Mint tokens to cToken
- client-transfer-interface.rs - SPL to cToken transfers
- client-close-ctoken.rs - Close cToken account

Rename ctoken/ to c-token/ and add proper Cargo.toml with
git dependencies pinned to commit 3b811efce.

Author: tilo-14

README.md

@@ -42,7 +42,16 @@ Full compressed account lifecycle (create, increment, decrement, reset, close):
 
 - **[zk-id](./zk-id)** - A minimal zk id Solana program that uses zero-knowledge proofs for identity verification with compressed accounts.
 
-  
+### Compressed Token (c-token) Examples
+
+- **[c-token](./c-token/)** - Client examples for compressed tokens (cToken) including:
+  - Create compressed mint (cMint) with metadata
+  - Create compressed token account (cToken)
+  - Create compressed associated token account (cATA)
+  - Mint tokens to cToken account
+  - Transfer between SPL and cToken accounts
+  - Close cToken account
+
 ## Light Protocol dependencies
 
 ### Rust Crates