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/store/settings.go

@@ -0,0 +1,69 @@
+package store
+
+import (
+	"database/sql"
+	"fmt"
+	"strconv"
+
+	"github.com/local-mcp/local-mcp-go/internal/models"
+)
+
+// SettingsStore reads and writes the settings table.
+type SettingsStore struct {
+	db *sql.DB
+}
+
+// NewSettingsStore creates a SettingsStore backed by db.
+func NewSettingsStore(db *sql.DB) *SettingsStore {
+	return &SettingsStore{db: db}
+}
+
+// Get returns the current settings.
+func (s *SettingsStore) Get() (models.Settings, error) {
+	rows, err := s.db.Query(`SELECT key, value FROM settings`)
+	if err != nil {
+		return models.Settings{}, fmt.Errorf("get settings: %w", err)
+	}
+	defer rows.Close()
+
+	cfg := models.Settings{
+		DefaultWaitSeconds:     10,
+		AgentStaleAfterSeconds: 30,
+	}
+
+	for rows.Next() {
+		var key, value string
+		if err := rows.Scan(&key, &value); err != nil {
+			return cfg, err
+		}
+		switch key {
+		case "default_wait_seconds":
+			if n, err := strconv.Atoi(value); err == nil {
+				cfg.DefaultWaitSeconds = n
+			}
+		case "default_empty_response":
+			cfg.DefaultEmptyResponse = value
+		case "agent_stale_after_seconds":
+			if n, err := strconv.Atoi(value); err == nil {
+				cfg.AgentStaleAfterSeconds = n
+			}
+		}
+	}
+	return cfg, rows.Err()
+}
+
+// Update saves settings. Only non-nil fields are updated; pass a partial
+// struct pointer using the Patch helper below.
+func (s *SettingsStore) Update(patch models.Settings) error {
+	_, err := s.db.Exec(`
+		INSERT OR REPLACE INTO settings (key, value) VALUES
+		('default_wait_seconds',      ?),
+		('default_empty_response',    ?),
+		('agent_stale_after_seconds', ?)`,
+		strconv.Itoa(patch.DefaultWaitSeconds),
+		patch.DefaultEmptyResponse,
+		strconv.Itoa(patch.AgentStaleAfterSeconds),
+	)
+	return err
+}
+