Fix docs pages that no longer match the code

Samples that did not compile or run as shown:
- res.user_data.get<T>() inside a generic lambda needs the `template`
  keyword; use explicit parameter types (tour 09, cookbook s15).
- listen() on a Unix domain socket fails with port 0 (tour 09, s22).
- "*.dev.local" is not a NO_PROXY pattern (c16).
- ssl_backend_error() holds a verify result, not an ERR_get_error()
  value, after a verification failure; decode each with the matching
  OpenSSL function (c18).
- The content provider's `length` is everything that remains, so the
  sample read the whole file in one call (s05).

Statements corrected:
- Client keep-alive is off by default; c14 is rewritten around
  set_keep_alive(true).
- Mounted files are looked up before GET handlers (tour 04, s04).
- Params keep insertion order, and to_string(Error::Connection) reads
  "Could not establish connection" (tour 02).
- A chunked provider ends with sink.done(), and post_routing_handler
  runs before the response is sent (tour 09).
- Timeouts surface as Error::Read; Error::Timeout comes from the stream
  API (c17). The max timeout cuts off the wait for the response only
  (c13). The progress callback needs Content-Length (c11).
- Encoding selection follows q-values, then Brotli, gzip, Zstd (s08),
  and the client compresses with the first of those it was built with
  (c15).
- stop() cuts a provider-driven response short (s19); a rejected
  content_reader already gets 400 or 413 (s07); user_data values must be
  copyable (s12); Client accepts a client certificate too (t04);
  on_message() is the fallback for every unhandled event and 204/403/404
  end reconnection (e04); the pong timeout takes two to three intervals
  and ends a waiting read() (w02).

In the LLM app tutorial, an uncaught exception does not crash the
server, so say what it does instead. Drop the server and client timeout
settings whose stated purpose, covering inference and download time,
they do not serve: those timeouts bound a single socket wait. Update
the llama.cpp server layout in chapter 7.

docs-src/pages/en/cookbook/c15-compression.md

@@ -28,7 +28,7 @@ std::string big_payload = build_payload();
 auto res = cli.Post("/api/data", big_payload, "application/json");
 ```
 
-With `set_compress(true)`, the body of POST or PUT requests gets gzipped before sending. The server needs to handle compressed bodies too.
+With `set_compress(true)`, the body of POST or PUT requests is compressed before sending. The encoding is the first one enabled in your build, in the order Brotli, gzip, Zstd. The server needs to handle compressed bodies too.
 
 ## Decompress the response
 
@@ -44,4 +44,4 @@ With `set_decompress(true)`, the client automatically decompresses responses tha
 
 It's on by default, so normally you don't need to do anything. Set it to `false` only if you want the raw compressed bytes.
 
-> **Warning:** If you build without `CPPHTTPLIB_ZLIB_SUPPORT`, calling `set_compress()` or `set_decompress()` does nothing. If compression isn't working, check the macro definition first.
+> **Warning:** If you build without any compression library, `set_compress(true)` leaves the request uncompressed. And a response compressed with an encoding your build lacks makes the request fail with `Error::UnsupportedContentEncoding`. If compression isn't working, check the macro definitions first.