feat(logging): integrate slog logging with env control and request/sync tracing

- Configure structured slog logger in cmd/server/main.go via LOG_LEVEL and DEBUG env vars
- Add HTTP API request logging middleware in internal/api/ with status and duration_ms
- Add WebSocket join/leave, event reception, and debounced SQLite flush tracing in docroom
- Document LOG_LEVEL and DEBUG settings in .env.example, compose.yaml, and docker-compose.yml

internal/config/config.go

@@ -1,6 +1,7 @@
 package config
 
 import (
+	"log/slog"
 	"os"
 	"path/filepath"
 	"strings"
@@ -14,6 +15,7 @@ type Config struct {
 	BaseURL           string
 	AllowRegistration bool
 	LogLevel          string
+	Debug             bool
 	DemoMode          bool
 
 	// Optional SMTP environment variables (can also be overridden/configured in DB system_settings)
@@ -40,7 +42,14 @@ func Load() *Config {
 	jwtSecret := getEnv("JWT_SECRET", "mindsift-default-selfhosted-jwt-secret-key-2026")
 	baseURL := getEnv("BASE_URL", "http://localhost:"+port)
 	allowReg := strings.ToLower(getEnv("ALLOW_REGISTRATION", "false")) == "true"
-	logLevel := getEnv("LOG_LEVEL", "info")
+
+	debugVal := strings.ToLower(getEnv("DEBUG", "false"))
+	debug := debugVal == "true" || debugVal == "1" || debugVal == "yes" || debugVal == "on"
+
+	logLevel := strings.ToLower(getEnv("LOG_LEVEL", "info"))
+	if debug {
+		logLevel = "debug"
+	}
 
 	demoVal := strings.ToLower(getEnv("MINDA_DEMO", getEnv("MINDSIFT_DEMO", getEnv("DEMO_MODE", "false"))))
 	demoMode := demoVal == "true" || demoVal == "1" || demoVal == "yes" || demoVal == "on"
@@ -60,6 +69,7 @@ func Load() *Config {
 		BaseURL:           baseURL,
 		AllowRegistration: allowReg,
 		LogLevel:          logLevel,
+		Debug:             debug,
 		DemoMode:          demoMode,
 		SMTPHost:          smtpHost,
 		SMTPPort:          smtpPort,
@@ -70,6 +80,20 @@ func Load() *Config {
 	}
 }
 
+// SlogLevel parses Config.LogLevel into a standard slog.Level.
+func (c *Config) SlogLevel() slog.Level {
+	switch strings.ToLower(strings.TrimSpace(c.LogLevel)) {
+	case "debug":
+		return slog.LevelDebug
+	case "warn", "warning":
+		return slog.LevelWarn
+	case "error":
+		return slog.LevelError
+	default:
+		return slog.LevelInfo
+	}
+}
+
 func getEnv(key, fallback string) string {
 	if val, ok := os.LookupEnv(key); ok && strings.TrimSpace(val) != "" {
 		return strings.TrimSpace(val)