Sprint 6: JSON file persistence + real SSH terminal + V1 crypto/knownhosts integration

- go.mod replace directive for git.tukangketik.id/swanadiva/hostkeeper → ../../v1
- store/ package: JSON file persistence for hosts, snippets, keys, settings
  (~/Library/Application Support/hostkeeper/v2/)
- model SSH fields: Hostname, Port, Username, AuthType, Password, KeyID
- sshconn/ package: real SSH client via golang.org/x/crypto/ssh
- Terminal WS: real SSH connection with fallback to mock shell
- Dynamic host list in terminal (server-rendered JSON script tag)
- All mock data defaults removed from model packages
- Settings persist via store/settings.go

app/backend/internal/store/snippet.go

@@ -0,0 +1,70 @@
+package store
+
+import (
+	"time"
+	"git.tukangketik.id/swanadiva/hostkeeper/v2/internal/model"
+)
+
+type SnippetStore struct {
+	snippets []model.Snippet
+}
+
+func NewSnippetStore() *SnippetStore {
+	s := &SnippetStore{}
+	mu.RLock()
+	readFile("snippets.json", &s.snippets)
+	mu.RUnlock()
+	if s.snippets == nil {
+		s.snippets = []model.Snippet{}
+	}
+	return s
+}
+
+func (s *SnippetStore) All() []model.Snippet {
+	mu.RLock()
+	defer mu.RUnlock()
+	return s.snippets
+}
+
+func (s *SnippetStore) Search(q string) []model.Snippet {
+	mu.RLock()
+	defer mu.RUnlock()
+	if q == "" {
+		return s.snippets
+	}
+	var res []model.Snippet
+	for _, sn := range s.snippets {
+		if contains(sn.Name, q) || contains(sn.Content, q) || contains(sn.Language, q) {
+			res = append(res, sn)
+		}
+	}
+	return res
+}
+
+func (s *SnippetStore) Add(name, content, language string, tags []string) model.Snippet {
+	mu.Lock()
+	defer mu.Unlock()
+	sn := model.Snippet{
+		ID:        randID(),
+		Name:      name,
+		Content:   content,
+		Language:  language,
+		Tags:      tags,
+		CreatedAt: time.Now().Format("Jan 2, 2006"),
+	}
+	s.snippets = append(s.snippets, sn)
+	writeFile("snippets.json", &s.snippets)
+	return sn
+}
+
+func (s *SnippetStore) Delete(id string) {
+	mu.Lock()
+	defer mu.Unlock()
+	for i, sn := range s.snippets {
+		if sn.ID == id {
+			s.snippets = append(s.snippets[:i], s.snippets[i+1:]...)
+			writeFile("snippets.json", &s.snippets)
+			return
+		}
+	}
+}