v0.6.1: Code review bugfixes — 7 correctness/safety/quality fixes

- Fix http.NotFound(w, nil) → pass actual request in handlers
- Fix dashboard running/stopped counts to match displayed stacks
- Fix Secure cookie blocking HTTP login (dynamic based on request)
- Remove misleading subtle.ConstantTimeCompare in session check
- Fix cleanupSessions goroutine leak (proper ticker + done channel)
- Add http.MaxBytesReader (1MB) to API POST endpoints
- Cache time.LoadLocation("Europe/Budapest") in template funcmap

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

controller/internal/web/funcmap.go

@@ -12,6 +12,11 @@ import (
 
 // templateFuncMap returns the FuncMap used by all HTML templates.
 func (s *Server) templateFuncMap() template.FuncMap {
+	loc, err := time.LoadLocation("Europe/Budapest")
+	if err != nil {
+		loc = time.UTC
+	}
+
 	return template.FuncMap{
 		"stateColor": func(state stacks.ContainerState) string {
 			switch state {
@@ -164,10 +169,6 @@ func (s *Server) templateFuncMap() template.FuncMap {
 			if t.IsZero() {
 				return "–"
 			}
-			loc, _ := time.LoadLocation("Europe/Budapest")
-			if loc == nil {
-				loc = time.UTC
-			}
 			now := time.Now().In(loc)
 			d := now.Sub(t.In(loc))
 			switch {
@@ -187,20 +188,12 @@ func (s *Server) templateFuncMap() template.FuncMap {
 			if t.IsZero() {
 				return "–"
 			}
-			loc, _ := time.LoadLocation("Europe/Budapest")
-			if loc == nil {
-				loc = time.UTC
-			}
 			return t.In(loc).Format("2006-01-02 15:04")
 		},
 		"fmtTimeShort": func(t time.Time) string {
 			if t.IsZero() {
 				return "–"
 			}
-			loc, _ := time.LoadLocation("Europe/Budapest")
-			if loc == nil {
-				loc = time.UTC
-			}
 			lt := t.In(loc)
 			now := time.Now().In(loc)
 			if lt.Year() == now.Year() && lt.YearDay() == now.YearDay() {
@@ -222,10 +215,6 @@ func (s *Server) templateFuncMap() template.FuncMap {
 			if t.IsZero() {
 				return "–"
 			}
-			loc, _ := time.LoadLocation("Europe/Budapest")
-			if loc == nil {
-				loc = time.UTC
-			}
 			lt := t.In(loc)
 			now := time.Now().In(loc)
 			timeStr := lt.Format("15:04")
@@ -250,10 +239,6 @@ func (s *Server) templateFuncMap() template.FuncMap {
 			}
 		},
 		"nextPruneLabel": func(schedule string) string {
-			loc, _ := time.LoadLocation("Europe/Budapest")
-			if loc == nil {
-				loc = time.UTC
-			}
 			now := time.Now().In(loc)
 			var next time.Time
 			switch strings.ToLower(schedule) {