feat(ui): add a progress loading screen and lazy project list

The loading screen shows live scan progress from the server, with a pulsing outline of the dashboard. The server now reports how many repositories the running scan has finished.

The project list renders 20 rows first and adds more as the end scrolls into view. Groups on very wide screens fill two balanced columns, the fact figures sit in a row under the health strip, and the headline counts match the rows listed below it.

internal/collector/collector.go

@@ -33,6 +33,9 @@ type View struct {
 	Warn        int
 	Loaded      bool
 	Refreshing  bool
+	// ScanDone and ScanTotal count the repos of the running (or last) scan.
+	ScanDone  int
+	ScanTotal int
 }
 
 // Stats are monotonic counters and timings of the refresh loop.
@@ -56,6 +59,8 @@ type Collector struct {
 	th          config.Thresholds
 	interval    time.Duration
 	refreshes   atomic.Uint64
+	scanDone    atomic.Int64
+	scanTotal   atomic.Int64
 	repoErrs    atomic.Uint64
 	lastDur     time.Duration
 	concurrency int
@@ -118,6 +123,8 @@ func (c *Collector) Refresh(ctx context.Context) {
 
 	start := c.now()
 	c.limited.Store(false)
+	c.scanDone.Store(0)
+	c.scanTotal.Store(int64(len(c.names)))
 	results := make([]model.Repo, len(c.names))
 	sem := make(chan struct{}, c.concurrency)
 	var wg sync.WaitGroup
@@ -128,6 +135,7 @@ func (c *Collector) Refresh(ctx context.Context) {
 			defer wg.Done()
 			defer func() { <-sem }()
 			results[i] = c.refreshOne(ctx, name, start)
+			c.scanDone.Add(1)
 		}()
 	}
 	wg.Wait()
@@ -193,6 +201,7 @@ func (c *Collector) View() View {
 	v := View{
 		Now: now, LastRefresh: c.lastRefresh, Interval: c.interval, Thresholds: c.th,
 		Loaded: c.loaded, Refreshing: c.refreshing.Load(),
+		ScanDone: int(c.scanDone.Load()), ScanTotal: int(c.scanTotal.Load()),
 	}
 	v.Repos = make([]model.Repo, 0, len(c.names))
 	for _, n := range c.names {

internal/collector/collector_test.go

@@ -312,3 +312,28 @@ func TestSummarizeWarningsMergesSharedReason(t *testing.T) {
 		t.Fatalf("got %q", got)
 	}
 }
+
+func TestScanProgressAdvancesAsReposFinish(t *testing.T) {
+	release := make(chan struct{})
+	started := make(chan struct{}, 4)
+	f := &fakeFetcher{fn: func(name string) (model.Repo, error) {
+		started <- struct{}{}
+		<-release
+		return model.Repo{FullName: name}, nil
+	}}
+	c := newCollector(f, "o/a", "o/b", "o/c")
+	if v := c.View(); v.ScanDone != 0 || v.ScanTotal != 0 {
+		t.Fatalf("before any scan: %+v", v)
+	}
+	done := make(chan struct{})
+	go func() { c.Refresh(context.Background()); close(done) }()
+	<-started
+	if v := c.View(); v.ScanTotal != 3 || v.ScanDone != 0 || !v.Refreshing {
+		t.Fatalf("during scan: done=%d total=%d refreshing=%v", v.ScanDone, v.ScanTotal, v.Refreshing)
+	}
+	close(release)
+	<-done
+	if v := c.View(); v.ScanDone != 3 || v.ScanTotal != 3 {
+		t.Fatalf("after scan: done=%d total=%d", v.ScanDone, v.ScanTotal)
+	}
+}