Configurable --network providers docs (#3875)

<!-- Reference any GitHub issues resolved by this PR -->

Towards #3765

Stack: 
- #3874
- #3875 ⬅

## Introduced changes

<!-- A brief description of the changes -->

- Documentation to configurable `--network` providers

## Checklist

<!-- Make sure all of these are complete -->

- [x] Linked relevant issue
- [x] Updated relevant documentation
- [x] Added relevant tests
- [x] Performed self-review of the code
- [x] Added changes to `CHANGELOG.md`

---------

Co-authored-by: Franciszek Job <[email protected]>

Author: MKowalski8

CHANGELOG.md

@@ -17,6 +17,12 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 - A bug that prevented the `#[test_case]` attribute from being used on its own with cheatcodes
 
+### Cast
+
+#### Added 
+
+- Possibility to configure urls of predefined networks used by `--network` flag via `sncast` profile in `snfoundry.toml`
+
 ## [0.51.2] - 2025-10-31
 
 ### Cast

docs/src/appendix/snfoundry-toml.md

@@ -90,6 +90,19 @@ The `block-explorer` field specifies the block explorer service used to display
 block-explorer = "StarkScan"
 ```
 
+#### `[sncast.<profile-name>.networks]`
+
+The URLs of the predefined networks can be configured.
+When you use `--network <network_name>`, `sncast` first checks whether you have a custom URL configured for that network.
+In the absence of a user-defined value, the default configuration is applied - public RPC provider is used for `mainnet` and `sepolia`, and the `devnet` endpoint is determined automatically.
+
+```toml
+[sncast.myprofile.networks]
+mainnet = "https://mainnet.your-node.com"
+sepolia = "https://sepolia.your-node.com"
+devnet = "http://127.0.0.1:5050"
+```
+
 #### Complete Example of `snfoundry.toml` File
 
 ```toml
@@ -102,6 +115,11 @@ wait-params = { timeout = 500, retry-interval = 10 }
 block-explorer = "StarkScan"
 show-explorer-links = true
 
+[sncast.myprofile1.networks]
+mainnet = "https://mainnet.your-node.com"
+sepolia = "https://sepolia.your-node.com"
+devnet = "http://127.0.0.1:5050"
+
 [sncast.dev]
 url = "http://127.0.0.1:5056/rpc"
 account = "devuser"

docs/src/starknet/sncast-overview.md

@@ -71,6 +71,9 @@ For **devnet**, `sncast` will try to detect running `starknet-devnet` instance a
 If using `sncast` extensively, we recommend getting access to a dedicated RPC node and providing its URL to sncast with
 `--url` flag.
 
+> 📝 **Note**
+> You can configure URLs for predefined networks (used by the `--network` flag) in `snfoundry.toml` profiles. Read more in [snfoundry.toml Reference](../appendix/snfoundry-toml.md#sncastprofile-namenetworks).
+
 ### Arguments
 
 Some `sncast` commands (namely `call`, `deploy` and `invoke`) allow passing arguments to perform an action with on the blockchain.