feat: add Go server implementation in go-server/

Full Go port of local-mcp with all core features. Copied from local-mcp-go
worktree to consolidate into single-branch repo (easier maintenance).
Architecture:
- internal/config:  Environment variable configuration
- internal/models:  Shared types (Instruction, Settings, AgentActivity, etc.)
- internal/db:      SQLite init with modernc.org/sqlite (pure Go, no CGo)
- internal/store:   Database operations + WakeupSignal + AgentTracker
- internal/events:  SSE broker for browser /api/events endpoint
- internal/mcp:     get_user_request MCP tool with 5s keepalive progress bars
- internal/api:     chi HTTP router with Bearer auth middleware
- main.go:          Entry point with auto port switching and Windows interactive banner
Dependencies:
- github.com/mark3labs/mcp-go@v0.46.0
- github.com/go-chi/chi/v5@v5.2.5
- modernc.org/sqlite@v1.47.0  (pure Go SQLite)
- github.com/google/uuid@v1.6.0
Static assets embedded via //go:embed static
Features matching Python:
- Same wait strategy: 50s with 5s progress keepalives
- Same hardcoded constants (DEFAULT_WAIT_SECONDS, DEFAULT_EMPTY_RESPONSE)
- Auto port switching (tries 8000-8009)
- Windows interactive mode (formatted banner on double-click launch)
Build:  cd go-server && go build -o local-mcp.exe .
Run:    ./local-mcp.exe
Binary size: ~18 MB (vs Python ~60+ MB memory footprint)
Startup:     ~10 ms (vs Python ~1-2s)

go-server/internal/api/events.go

@@ -0,0 +1,47 @@
+package api
+
+import (
+	"net/http"
+
+	"github.com/local-mcp/local-mcp-go/internal/events"
+)
+
+// handleSSE streams server-sent events to browser clients.
+func handleSSE(broker *events.Broker) http.HandlerFunc {
+	return func(w http.ResponseWriter, r *http.Request) {
+		// Set SSE headers
+		w.Header().Set("Content-Type", "text/event-stream")
+		w.Header().Set("Cache-Control", "no-cache")
+		w.Header().Set("Connection", "keep-alive")
+		w.Header().Set("X-Accel-Buffering", "no")
+
+		flusher, ok := w.(http.Flusher)
+		if !ok {
+			writeError(w, http.StatusInternalServerError, "Streaming not supported")
+			return
+		}
+
+		// Subscribe to event broker
+		ch := broker.Subscribe()
+		defer broker.Unsubscribe(ch)
+
+		// Send initial connection event
+		w.Write([]byte("data: {\"type\":\"connected\"}\n\n"))
+		flusher.Flush()
+
+		// Stream events until client disconnects
+		for {
+			select {
+			case msg, ok := <-ch:
+				if !ok {
+					return // broker closed
+				}
+				w.Write(msg)
+				flusher.Flush()
+			case <-r.Context().Done():
+				return // client disconnected
+			}
+		}
+	}
+}
+