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/idlewatcher/html/loading.js

@@ -0,0 +1,80 @@
+let ready = false;
+
+window.onload = async function () {
+  const consoleEl = document.getElementById("console");
+  const loadingDotsEl = document.getElementById("loading-dots");
+
+  function formatTimestamp(timestamp) {
+    const date = new Date(timestamp);
+    return date.toLocaleTimeString("en-US", {
+      hour12: false,
+      hour: "2-digit",
+      minute: "2-digit",
+      second: "2-digit",
+      fractionalSecondDigits: 3,
+    });
+  }
+
+  function addConsoleLine(type, message, timestamp) {
+    const line = document.createElement("div");
+    line.className = `console-line ${type}`;
+
+    const timestampEl = document.createElement("span");
+    timestampEl.className = "console-timestamp";
+    timestampEl.textContent = formatTimestamp(timestamp);
+
+    const messageEl = document.createElement("span");
+    messageEl.className = "console-message";
+    messageEl.textContent = message;
+
+    line.appendChild(timestampEl);
+    line.appendChild(messageEl);
+
+    consoleEl.appendChild(line);
+    consoleEl.scrollTop = consoleEl.scrollHeight;
+  }
+
+  // Connect to SSE endpoint
+  const eventSource = new EventSource(wakeEventsPath);
+
+  eventSource.onmessage = function (event) {
+    const data = JSON.parse(event.data);
+
+    if (data.type === "ready") {
+      ready = true;
+      // Container is ready, hide loading dots and refresh
+      loadingDotsEl.style.display = "none";
+      addConsoleLine(
+        data.type,
+        "Container is ready, refreshing...",
+        data.timestamp
+      );
+      setTimeout(() => {
+        window.location.reload();
+      }, 200);
+    } else if (data.type === "error") {
+      // Show error message and hide loading dots
+      const errorMessage = data.error || data.message;
+      addConsoleLine(data.type, errorMessage, data.timestamp);
+      loadingDotsEl.style.display = "none";
+      eventSource.close();
+    } else {
+      // Show other message types
+      addConsoleLine(data.type, data.message, data.timestamp);
+    }
+  };
+
+  eventSource.onerror = function (event) {
+    if (ready) {
+      // event will be closed by the server
+      return;
+    }
+    addConsoleLine(
+      "error",
+      "Connection lost. Please refresh the page.",
+      new Date().toISOString()
+    );
+    loadingDotsEl.style.display = "none";
+    eventSource.close();
+  };
+};