fix: resolve file library Open File bug, upload reliability, and SSE proxy timeouts (#203)

The Open File button in the Files section did nothing due to a race
condition where the home page reset the file store on mount before files
from handleOpenFile could render. Upload on the files page used fetch
with no timeout, progress, or retry, causing silent failures on mobile
and slow connections. SSE connections for job progress had no keepalive
pings, allowing reverse proxies to kill idle streams.

apps/docs/guide/deployment.md

@@ -367,6 +367,22 @@ labels:
   - "traefik.http.routers.snapotter.middlewares=snapotter-body"
 ```
 
+### Caddy
+
+```caddyfile
+images.example.com {
+    reverse_proxy localhost:1349 {
+        flush_interval -1
+        transport http {
+            read_timeout 300s
+            write_timeout 300s
+        }
+    }
+}
+```
+
+`flush_interval -1` disables response buffering, which is required for SSE progress events (batch processing, AI tools, feature installs). The extended timeouts allow large file uploads to complete without Caddy closing the connection early.
+
 ### Cloudflare Tunnels
 
 ```bash