feat(idlewatcher): implement real-time SSE-based loading page with enhanced UX

This major overhaul of the idlewatcher system introduces a modern, real-time loading experience with Server-Sent Events (SSE) streaming and improved error handling.

- **Real-time Event Streaming**: New SSE endpoint (`/$godoxy/wake-events`) provides live updates during container wake process
- **Enhanced Loading Page**: Modern console-style interface with timestamped events and color-coded status messages
- **Improved Static Asset Management**: Dedicated paths for CSS, JS, and favicon to avoid conflicting with upstream assets
- **Event History Buffer**: Stores wake events for reconnecting clients and debugging

- Refactored HTTP request handling with cleaner static asset routing
- Added `WakeEvent` system with structured event types (starting, waking_dep, dep_ready, container_woke, waiting_ready, ready, error)
- Implemented thread-safe event broadcasting using xsync.Map for concurrent SSE connections
- Enhanced error handling with detailed logging and user-friendly error messages
- Simplified loading page template system with better asset path management
- Fixed race conditions in dependency waking and state management

- Removed `common.go` functions (canceled, waitStarted) - moved inline for better context
- Updated Waker interface to accept context parameter in Wake() method
- New static asset paths use `/$godoxy/` prefix to avoid conflicts

- Console-style output with Fira Code font for better readability
- Color-coded event types (yellow for starting, blue for dependencies, green for success, red for errors)
- Automatic page refresh when container becomes ready
- Improved visual design with better glassmorphism effects and responsive layout
- Real-time progress feedback during dependency wake and container startup

This change transforms the static loading page into a dynamic, informative experience that keeps users informed during the wake process while maintaining backward compatibility with existing routing behavior.

internal/net/gphttp/loadbalancer/loadbalancer.go

@@ -8,11 +8,12 @@ import (
 
 	"github.com/rs/zerolog"
 	"github.com/rs/zerolog/log"
+	idlewatcher "github.com/yusing/godoxy/internal/idlewatcher/types"
 	"github.com/yusing/godoxy/internal/types"
 	"github.com/yusing/godoxy/internal/utils/pool"
 	gperr "github.com/yusing/goutils/errs"
-	"github.com/yusing/goutils/http/httpheaders"
 	"github.com/yusing/goutils/task"
+	"golang.org/x/sync/errgroup"
 )
 
 // TODO: stats of each server.
@@ -218,14 +219,20 @@ func (lb *LoadBalancer) ServeHTTP(rw http.ResponseWriter, r *http.Request) {
 		http.Error(rw, "Service unavailable", http.StatusServiceUnavailable)
 		return
 	}
-	if r.Header.Get(httpheaders.HeaderGoDoxyCheckRedirect) != "" {
+	if r.URL.Path == idlewatcher.WakeEventsPath {
+		var errs errgroup.Group
 		// wake all servers
 		for _, srv := range srvs {
-			if err := srv.TryWake(); err != nil {
-				lb.l.Warn().Err(err).
-					Str("server", srv.Name()).
-					Msg("failed to wake server")
-			}
+			errs.Go(func() error {
+				err := srv.TryWake()
+				if err != nil {
+					return fmt.Errorf("failed to wake server %q: %w", srv.Name(), err)
+				}
+				return nil
+			})
+		}
+		if err := errs.Wait(); err != nil {
+			gperr.LogWarn("failed to wake some servers", err, &lb.l)
 		}
 	}
 	lb.impl.ServeHTTP(srvs, rw, r)

internal/net/gphttp/loadbalancer/server.go

@@ -1,6 +1,7 @@
 package loadbalancer
 
 import (
+	"context"
 	"net/http"
 
 	idlewatcher "github.com/yusing/godoxy/internal/idlewatcher/types"
@@ -66,7 +67,7 @@ func (srv *server) String() string {
 func (srv *server) TryWake() error {
 	waker, ok := srv.Handler.(idlewatcher.Waker)
 	if ok {
-		return waker.Wake()
+		return waker.Wake(context.Background())
 	}
 	return nil
 }