fix: vídeo no app Linux travava a janela; abrir no player do sistema (0.3.2)

O AppImage traz o WebKitGTK sem os plugins de mídia do GStreamer; criar um <video>
derrubava o processo da página. O app Linux não cria mais <video>/<audio>: oferece
"Abrir no player do sistema". Clicar no preview abre a visualização grande.

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

crates/guara-core/src/http.rs

@@ -0,0 +1,103 @@
+//! Rotas HTTP de mídia (`/file` com Range e `/thumb`) compartilhadas pelo modo `guara ui`.
+
+use crate::service::Engine;
+use tiny_http::{Header, Method, Request, Response, StatusCode};
+
+pub fn header(name: &str, value: &str) -> Header {
+    Header::from_bytes(name.as_bytes(), value.as_bytes()).unwrap()
+}
+
+/// O cabeçalho Host bate com um dos endereços esperados (defesa contra DNS rebinding)?
+pub fn host_ok(req: &Request, hosts: &[String]) -> bool {
+    req.headers()
+        .iter()
+        .any(|h| h.field.equiv("Host") && hosts.iter().any(|x| x == h.value.as_str()))
+}
+
+/// Responde `/file/<job>/<id>` (com Range) e `/thumb/<job>/<id>?s=NNN`.
+/// Devolve a requisição quando ela não é uma rota de mídia.
+pub fn handle_media(eng: &Engine, token: &str, req: Request) -> Option<Request> {
+    let full = req.url().to_string();
+    let (path, query) = full.split_once('?').unwrap_or((full.as_str(), ""));
+    let is_file = path.starts_with("/file/");
+    let is_thumb = path.starts_with("/thumb/");
+    if !(is_file || is_thumb) {
+        return Some(req);
+    }
+    if req.method() == &Method::Options {
+        let r = Response::empty(204)
+            .with_header(header("Access-Control-Allow-Origin", "*"))
+            .with_header(header("Access-Control-Allow-Headers", "Range"))
+            .with_header(header("Access-Control-Allow-Methods", "GET, OPTIONS"));
+        let _ = req.respond(r);
+        return None;
+    }
+    if req.method() != &Method::Get {
+        let _ = req.respond(Response::from_string("método não permitido").with_status_code(405));
+        return None;
+    }
+    if !query
+        .split('&')
+        .any(|kv| kv.strip_prefix("t=") == Some(token))
+    {
+        let _ = req.respond(Response::from_string("token inválido").with_status_code(401));
+        return None;
+    }
+    let mut it = path
+        .trim_start_matches("/file/")
+        .trim_start_matches("/thumb/")
+        .split('/');
+    let (job, id) = (
+        it.next().unwrap_or(""),
+        it.next().and_then(|s| s.parse::<u64>().ok()),
+    );
+    let Some(id) = id else {
+        let _ = req.respond(Response::from_string("id inválido").with_status_code(400));
+        return None;
+    };
+    if is_thumb {
+        let size = query
+            .split('&')
+            .find_map(|kv| kv.strip_prefix("s="))
+            .and_then(|v| v.parse::<u32>().ok())
+            .unwrap_or(256);
+        match eng.thumb(job, id, size) {
+            Ok(bytes) => {
+                let r = Response::from_data(bytes.as_ref().clone())
+                    .with_header(header("Content-Type", "image/jpeg"))
+                    .with_header(header("Cache-Control", "private, max-age=3600"))
+                    .with_header(header("Access-Control-Allow-Origin", "*"));
+                let _ = req.respond(r);
+            }
+            Err(code) => {
+                let _ = req.respond(
+                    Response::from_string("sem miniatura")
+                        .with_status_code(code)
+                        .with_header(header("Access-Control-Allow-Origin", "*")),
+                );
+            }
+        }
+        return None;
+    }
+    let range = req
+        .headers()
+        .iter()
+        .find(|h| h.field.equiv("Range"))
+        .map(|h| h.value.as_str().to_string());
+    match eng.file_slice(job, id, range.as_deref()) {
+        Ok(slice) => {
+            let (status, len) = (slice.status(), slice.len() as usize);
+            let headers: Vec<Header> = slice.headers().iter().map(|(k, v)| header(k, v)).collect();
+            let resp = Response::new(StatusCode(status), headers, slice.reader(), Some(len), None);
+            let _ = req.respond(resp);
+        }
+        Err(code) => {
+            let _ = req.respond(
+                Response::from_string("indisponível")
+                    .with_status_code(code)
+                    .with_header(header("Access-Control-Allow-Origin", "*")),
+            );
+        }
+    }
+    None
+}