feat(maintenance): add policy executor and config provider

ConfigProvider, PolicyExecutor, DBStatsProvider, scheduler и safety; зависимость robfig/cron/v3.

Co-authored-by: Cursor <[email protected]>

internal/maintenance/config_provider.go

@@ -0,0 +1,67 @@
+package maintenance
+
+import (
+	"context"
+	"sync"
+
+	"evobgp/internal/store"
+)
+
+// ConfigProvider caches maintenance policies from store.Backend with hot reload.
+type ConfigProvider struct {
+	store store.Backend
+	mu    sync.RWMutex
+	items []*store.MaintenancePolicy
+}
+
+// NewConfigProvider constructs a provider; call Reload before use.
+func NewConfigProvider(st store.Backend) *ConfigProvider {
+	return &ConfigProvider{store: st}
+}
+
+// Reload loads all policies from the database into memory.
+func (c *ConfigProvider) Reload(ctx context.Context) error {
+	if c == nil || c.store == nil {
+		return nil
+	}
+	_ = ctx
+	items, _, _, err := c.store.ListMaintenancePolicies("", 1000)
+	if err != nil {
+		return err
+	}
+	cp := make([]*store.MaintenancePolicy, len(items))
+	copy(cp, items)
+	c.mu.Lock()
+	c.items = cp
+	c.mu.Unlock()
+	return nil
+}
+
+// Snapshot returns a copy of cached policies.
+func (c *ConfigProvider) Snapshot() []*store.MaintenancePolicy {
+	if c == nil {
+		return nil
+	}
+	c.mu.RLock()
+	defer c.mu.RUnlock()
+	out := make([]*store.MaintenancePolicy, len(c.items))
+	copy(out, c.items)
+	return out
+}
+
+// Get returns one policy by id from cache or store.
+func (c *ConfigProvider) Get(ctx context.Context, id string) (*store.MaintenancePolicy, error) {
+	if c == nil || c.store == nil {
+		return nil, store.ErrNotFound
+	}
+	c.mu.RLock()
+	for _, p := range c.items {
+		if p.ID == id {
+			cp := *p
+			c.mu.RUnlock()
+			return &cp, nil
+		}
+	}
+	c.mu.RUnlock()
+	return c.store.GetMaintenancePolicy(id)
+}