docs: fix broken markdown links and add lychee config

docs/sdk_developers/training/network_and_client.md

@@ -373,12 +373,10 @@ The Network and Client are separate but interdependent:
 2. **Client provides WHO and HOW**: The Client specifies who you are (operator credentials) and manages the actual communication
 3. **Together they enable communication**: The combination allows your application to securely interact with the Hedera blockchain
 
-## -### Example: Complete Setup
-
--```python
-+### Example: Complete Setup
+### Example: Complete Setup
 
 ```python
+
 from hiero_sdk_python.client.network import Network
 from hiero_sdk_python.client.client import Client
 from hiero_sdk_python.account.account_id import AccountId

pyproject.toml

@@ -147,3 +147,16 @@ skip-magic-trailing-comma = false
 
 [tool.ruff.lint.pydocstyle]
 convention = "google"
+
+[tool.lychee]
+exclude = [
+    "github.com/owner/repo",
+    "github.com/YOUR_",
+    "testnet.mirrornode.hedera.com/api/v1/transactions/0.0.123",
+    "localhost",
+    "github.com/user-attachments/assets/",
+]
+
+timeout = 20
+retry_wait_time = 2
+max_retries = 3