Add project scaffolding with fx DI, SQLite migrations, and healthcheck

- go.mod with git.eeqj.de/sneak/chat module
- internal packages: globals, logger, config, db, healthcheck, middleware, handlers, server
- SQLite database with embedded migration system (schema_migrations tracking)
- Migration 001: schema_migrations table
- Migration 002: channels table
- Config with chat-specific vars (MAX_HISTORY, SESSION_TIMEOUT, MAX_MESSAGE_SIZE, MOTD, SERVER_NAME, FEDERATION_KEY)
- Healthcheck endpoint at /.well-known/healthcheck.json
- Makefile, .gitignore
- cmd/chatd/main.go entry point

internal/healthcheck/healthcheck.go

@@ -0,0 +1,70 @@
+package healthcheck
+
+import (
+	"context"
+	"log/slog"
+	"time"
+
+	"git.eeqj.de/sneak/chat/internal/config"
+	"git.eeqj.de/sneak/chat/internal/db"
+	"git.eeqj.de/sneak/chat/internal/globals"
+	"git.eeqj.de/sneak/chat/internal/logger"
+	"go.uber.org/fx"
+)
+
+type HealthcheckParams struct {
+	fx.In
+	Globals  *globals.Globals
+	Config   *config.Config
+	Logger   *logger.Logger
+	Database *db.Database
+}
+
+type Healthcheck struct {
+	StartupTime time.Time
+	log         *slog.Logger
+	params      *HealthcheckParams
+}
+
+func New(lc fx.Lifecycle, params HealthcheckParams) (*Healthcheck, error) {
+	s := new(Healthcheck)
+	s.params = &params
+	s.log = params.Logger.Get()
+
+	lc.Append(fx.Hook{
+		OnStart: func(ctx context.Context) error {
+			s.StartupTime = time.Now()
+			return nil
+		},
+		OnStop: func(ctx context.Context) error {
+			return nil
+		},
+	})
+	return s, nil
+}
+
+type HealthcheckResponse struct {
+	Status        string `json:"status"`
+	Now           string `json:"now"`
+	UptimeSeconds int64  `json:"uptime_seconds"`
+	UptimeHuman   string `json:"uptime_human"`
+	Version       string `json:"version"`
+	Appname       string `json:"appname"`
+	Maintenance   bool   `json:"maintenance_mode"`
+}
+
+func (s *Healthcheck) uptime() time.Duration {
+	return time.Since(s.StartupTime)
+}
+
+func (s *Healthcheck) Healthcheck() *HealthcheckResponse {
+	resp := &HealthcheckResponse{
+		Status:        "ok",
+		Now:           time.Now().UTC().Format(time.RFC3339Nano),
+		UptimeSeconds: int64(s.uptime().Seconds()),
+		UptimeHuman:   s.uptime().String(),
+		Appname:       s.params.Globals.Appname,
+		Version:       s.params.Globals.Version,
+	}
+	return resp
+}