Fix broken relative links in cookbook docs (Fix #2490)

Cookbook body links referenced sibling pages with a bare slug
(e.g. `c14-keep-alive`). Under the pretty-URL layout each page lives
in its own directory, so these resolve against the page's own
directory and 404. Prefix them with `../` to match the convention
already used in the tour and llm-app sections.

Verified clean with `docs-gen check`.

Author: yhirose

docs-src/pages/en/cookbook/c01-get-response-body.md

@@ -57,4 +57,4 @@ Return `false` from the callback to abort the download. In the example above, if
 >
 > The `ResponseHandler` is called after headers arrive but before the body. Return `false` to skip the download entirely.
 
-> To show download progress, see [C11. Use the progress callback](c11-progress-callback).
+> To show download progress, see [C11. Use the progress callback](../c11-progress-callback).

docs-src/pages/en/cookbook/c02-json.md

@@ -31,6 +31,6 @@ if (res && res->status == 200) {
 
 `res->body` is a `std::string`, so you can pass it straight to your JSON library.
 
-> **Note:** Servers sometimes return HTML on errors. Check the status code before parsing to be safe. Some APIs also require an `Accept: application/json` header. If you're calling a JSON API repeatedly, [C03. Set default headers](c03-default-headers) can save you some boilerplate.
+> **Note:** Servers sometimes return HTML on errors. Check the status code before parsing to be safe. Some APIs also require an `Accept: application/json` header. If you're calling a JSON API repeatedly, [C03. Set default headers](../c03-default-headers) can save you some boilerplate.
 
-> For how to receive and return JSON on the server side, see [S02. Receive JSON requests and return JSON responses](s02-json-api).
+> For how to receive and return JSON on the server side, see [S02. Receive JSON requests and return JSON responses](../s02-json-api).

docs-src/pages/en/cookbook/c03-default-headers.md

@@ -52,4 +52,4 @@ auto res = cli.Get("/users", headers);
 
 Per-request headers are **added** on top of the defaults. Both are sent to the server.
 
-> For details on Bearer token auth, see [C06. Call an API with a Bearer token](c06-bearer-token).
+> For details on Bearer token auth, see [C06. Call an API with a Bearer token](../c06-bearer-token).

docs-src/pages/en/cookbook/c04-follow-location.md

@@ -35,4 +35,4 @@ Many sites redirect HTTP traffic to HTTPS. With `set_follow_location(true)` on,
 
 > **Warning:** To follow redirects to HTTPS, you need to build cpp-httplib with OpenSSL (or another TLS backend). Without TLS support, redirects to HTTPS will fail.
 
-> **Note:** Following redirects adds to the total request time. See [C12. Set timeouts](c12-timeouts) for timeout configuration.
+> **Note:** Following redirects adds to the total request time. See [C12. Set timeouts](../c12-timeouts) for timeout configuration.

docs-src/pages/en/cookbook/c05-basic-auth.md

@@ -43,4 +43,4 @@ For the more secure Digest authentication scheme, use `set_digest_auth()`. This
 cli.set_digest_auth("alice", "s3cret");
 ```
 
-> To call an API with a Bearer token, see [C06. Call an API with a Bearer token](c06-bearer-token).
+> To call an API with a Bearer token, see [C06. Call an API with a Bearer token](../c06-bearer-token).

docs-src/pages/en/cookbook/c06-bearer-token.md

@@ -47,4 +47,4 @@ if (res && res->status == 401) {
 
 > **Warning:** A Bearer token is itself a credential. Always send it over HTTPS, and never hard-code it into source or config files.
 
-> To set multiple headers at once, see [C03. Set default headers](c03-default-headers).
+> To set multiple headers at once, see [C03. Set default headers](../c03-default-headers).

docs-src/pages/en/cookbook/c07-multipart-upload.md

@@ -49,4 +49,4 @@ The arguments to `make_file_provider()` are `(form name, file path, file name, c
 
 > **Note:** You can mix `UploadFormDataItems` and `FormDataProviderItems` in the same request. A clean split is: text fields in `UploadFormDataItems`, files in `FormDataProviderItems`.
 
-> To show upload progress, see [C11. Use the progress callback](c11-progress-callback).
+> To show upload progress, see [C11. Use the progress callback](../c11-progress-callback).

docs-src/pages/en/cookbook/c08-post-file-body.md

@@ -31,4 +31,4 @@ If the file can't be opened, `make_file_body()` returns `size` as `0` and `provi
 
 > **Warning:** `make_file_body()` needs to fix the Content-Length up front, so it reads the file size ahead of time. If the file size might change mid-upload, this API isn't the right fit.
 
-> To send the file as multipart form data instead, see [C07. Upload a file as multipart form data](c07-multipart-upload).
+> To send the file as multipart form data instead, see [C07. Upload a file as multipart form data](../c07-multipart-upload).

docs-src/pages/en/cookbook/c09-chunked-upload.md

@@ -44,4 +44,4 @@ With a known size, the request carries a Content-Length header — so the server
 
 > **Detail:** `sink.write()` returns a `bool` indicating whether the write succeeded. If it returns `false`, the connection is gone — return `false` from the lambda to stop.
 
-> If you're just sending a file, `make_file_body()` is easier. See [C08. POST a file as raw binary](c08-post-file-body).
+> If you're just sending a file, `make_file_body()` is easier. See [C08. POST a file as raw binary](../c08-post-file-body).

docs-src/pages/en/cookbook/c10-stream-response.md

@@ -48,5 +48,5 @@ Accumulate into a buffer, then pull out and parse one line each time you see a n
 
 > **Warning:** When you pass a `ContentReceiver`, `res->body` stays **empty**. Store or process the body inside the callback yourself.
 
-> To track download progress, combine this with [C11. Use the progress callback](c11-progress-callback).
-> For Server-Sent Events (SSE), see [E04. Receive SSE on the client](e04-sse-client).
+> To track download progress, combine this with [C11. Use the progress callback](../c11-progress-callback).
+> For Server-Sent Events (SSE), see [E04. Receive SSE on the client](../e04-sse-client).