internal/server,shared: support request metadata (#850)

- add support for http handlers in the request chain to append metadata
to the request
- metrics middleware will include metadata in the activity log 
- update Activity UI to support metadata, drag sort columns
- update Activity UI capture dialog to use more screen space

Updates #834

internal/server/api.go

@@ -271,7 +271,7 @@ func (s *Server) startPreload() {
 			if err != nil {
 				continue
 			}
-			req = req.WithContext(shared.SetContext(req.Context(), shared.ReqContextData{Model: modelID, ModelID: modelID}))
+			req = req.WithContext(shared.SetContext(req.Context(), shared.ReqContextData{Model: modelID, ModelID: modelID, Metadata: make(map[string]string)}))
 
 			dw := &discardResponseWriter{status: http.StatusOK}
 			s.local.ServeHTTP(dw, req)
@@ -338,7 +338,7 @@ func (s *Server) handleUpstream(w http.ResponseWriter, r *http.Request) {
 	// Strip the /upstream/<model> prefix before forwarding.
 	r.URL.Path = remainingPath
 	// Pin the resolved model so the router skips body/query extraction.
-	*r = *r.WithContext(shared.SetContext(r.Context(), shared.ReqContextData{Model: searchName, ModelID: modelID}))
+	*r = *r.WithContext(shared.SetContext(r.Context(), shared.ReqContextData{Model: searchName, ModelID: modelID, Metadata: make(map[string]string)}))
 
 	switch {
 	case s.local.Handles(modelID):