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/host.go

@@ -0,0 +1,129 @@
+package store
+
+import "git.tukangketik.id/swanadiva/hostkeeper/v2/internal/model"
+
+type HostStore struct {
+	hosts []model.Host
+}
+
+func NewHostStore() *HostStore {
+	s := &HostStore{}
+	mu.RLock()
+	readFile("hosts.json", &s.hosts)
+	mu.RUnlock()
+	if s.hosts == nil {
+		s.hosts = []model.Host{}
+	}
+	return s
+}
+
+func (s *HostStore) All() []model.Host {
+	mu.RLock()
+	defer mu.RUnlock()
+	return s.hosts
+}
+
+func (s *HostStore) Search(q, filter string) []model.Host {
+	mu.RLock()
+	defer mu.RUnlock()
+	var result []model.Host
+	for _, h := range s.hosts {
+		if filter != "" && filter != "all" && h.Status != filter {
+			continue
+		}
+		if q == "" || contains(h.Name, q) || contains(h.IP, q) || contains(h.OS, q) ||
+			contains(h.Hostname, q) || contains(h.Username, q) {
+			result = append(result, h)
+		}
+	}
+	if result == nil {
+		return []model.Host{}
+	}
+	return result
+}
+
+func (s *HostStore) Get(id string) (model.Host, bool) {
+	mu.RLock()
+	defer mu.RUnlock()
+	for _, h := range s.hosts {
+		if h.ID == id {
+			return h, true
+		}
+	}
+	return model.Host{}, false
+}
+
+func (s *HostStore) Add(name, ip, os, provider, hostType string) model.Host {
+	return s.AddFull(model.Host{
+		Name:     name,
+		IP:       ip,
+		OS:       os,
+		Provider: provider,
+		Type:     hostType,
+	})
+}
+
+func (s *HostStore) AddFull(h model.Host) model.Host {
+	mu.Lock()
+	defer mu.Unlock()
+	if h.ID == "" {
+		h.ID = randID()
+	}
+	if h.Status == "" {
+		h.Status = "active"
+	}
+	s.hosts = append(s.hosts, h)
+	writeFile("hosts.json", &s.hosts)
+	return h
+}
+
+func (s *HostStore) Update(h model.Host) bool {
+	mu.Lock()
+	defer mu.Unlock()
+	for i, existing := range s.hosts {
+		if existing.ID == h.ID {
+			s.hosts[i] = h
+			writeFile("hosts.json", &s.hosts)
+			return true
+		}
+	}
+	return false
+}
+
+func (s *HostStore) Delete(id string) {
+	mu.Lock()
+	defer mu.Unlock()
+	for i, h := range s.hosts {
+		if h.ID == id {
+			s.hosts = append(s.hosts[:i], s.hosts[i+1:]...)
+			writeFile("hosts.json", &s.hosts)
+			return
+		}
+	}
+}
+
+func contains(s, q string) bool {
+	if len(s) < len(q) {
+		return false
+	}
+	for i := 0; i <= len(s)-len(q); i++ {
+		match := true
+		for j := 0; j < len(q); j++ {
+			sc, qc := s[i+j], q[j]
+			if sc >= 'A' && sc <= 'Z' {
+				sc += 32
+			}
+			if qc >= 'A' && qc <= 'Z' {
+				qc += 32
+			}
+			if sc != qc {
+				match = false
+				break
+			}
+		}
+		if match {
+			return true
+		}
+	}
+	return false
+}