Add 1d/7d/all time-range filter to admin by-model stats

By-model panel gains a segmented 1天/7天/全部 control. Selecting a
range fetches /api/stats?since=<RFC3339> and re-renders only that table
client-side, replicating the human/rate template helpers in JS; the
existing /api/stats since param already drives the server-side filter.

- internal/server/templates/admin.html: filter UI + JS, empty/loading states
- internal/server/server_test.go: render test for the filter controls
- scripts/test-instance.sh: build→start→stop→clean test-instance helper

internal/server/server_test.go

@@ -15,6 +15,7 @@ import (
 
 	"git.misaka.ren/M1saka/zhanlu_proxy/internal/auth"
 	"git.misaka.ren/M1saka/zhanlu_proxy/internal/config"
+	"git.misaka.ren/M1saka/zhanlu_proxy/internal/stats"
 	"git.misaka.ren/M1saka/zhanlu_proxy/internal/store"
 )
 
@@ -365,6 +366,47 @@ func TestModelTestNoCredentials(t *testing.T) {
 	}
 }
 
+// TestAdminRendersModelRangeFilter verifies the admin page renders without
+// panic for both empty and populated summaries, and that the by-model panel
+// carries the 1d/7d/all range filter controls and a client-renderable tbody.
+func TestAdminRendersModelRangeFilter(t *testing.T) {
+	populated := &stats.Summary{
+		PerModel: []stats.ModelStat{
+			{Model: "GLM-4.7", Requests: 3, PromptTokens: 10, CompletionTokens: 20, TotalTokens: 30, CachedTokens: 4},
+		},
+	}
+	cases := []struct {
+		name    string
+		summary *stats.Summary
+	}{
+		{"empty", &stats.Summary{}},
+		{"populated", populated},
+	}
+	for _, tc := range cases {
+		var buf bytes.Buffer
+		if err := adminTemplate.Execute(&buf, map[string]any{
+			"Enabled":         true,
+			"Stats":           tc.summary,
+			"DBPath":          "zhanlu.db",
+			"PasswordEnabled": false,
+		}); err != nil {
+			t.Fatalf("%s: render admin: %v", tc.name, err)
+		}
+		body := buf.String()
+		for _, want := range []string{
+			`id="model-range"`,
+			`data-range="1d"`,
+			`data-range="7d"`,
+			`data-range="all"`,
+			`id="model-tbody"`,
+		} {
+			if !strings.Contains(body, want) {
+				t.Fatalf("%s: admin output missing %q", tc.name, want)
+			}
+		}
+	}
+}
+
 // totNum extracts an int from a JSON-decoded numeric value (float64).
 func totNum(v any) int {
 	f, _ := v.(float64)