Add dashboard metrics, activity log, and dark theme

- Add DashboardMetrics for tracking downloads/uploads/cache hits per registry
- Add ActivityLog for recent activity with bounded size (50 entries)
- Instrument Docker, npm, Maven, and Cargo handlers with metrics
- Add /api/ui/dashboard endpoint with global stats and activity
- Implement dark theme dashboard with real-time polling (5s interval)
- Add mount points table showing registry paths and proxy upstreams

nora-registry/src/dashboard_metrics.rs

@@ -0,0 +1,114 @@
+use std::sync::atomic::{AtomicU64, Ordering};
+use std::time::Instant;
+
+/// Dashboard metrics for tracking registry activity
+/// Uses atomic counters for thread-safe access without locks
+pub struct DashboardMetrics {
+    // Global counters
+    pub downloads: AtomicU64,
+    pub uploads: AtomicU64,
+    pub cache_hits: AtomicU64,
+    pub cache_misses: AtomicU64,
+
+    // Per-registry download counters
+    pub docker_downloads: AtomicU64,
+    pub docker_uploads: AtomicU64,
+    pub npm_downloads: AtomicU64,
+    pub maven_downloads: AtomicU64,
+    pub maven_uploads: AtomicU64,
+    pub cargo_downloads: AtomicU64,
+    pub pypi_downloads: AtomicU64,
+
+    pub start_time: Instant,
+}
+
+impl DashboardMetrics {
+    pub fn new() -> Self {
+        Self {
+            downloads: AtomicU64::new(0),
+            uploads: AtomicU64::new(0),
+            cache_hits: AtomicU64::new(0),
+            cache_misses: AtomicU64::new(0),
+            docker_downloads: AtomicU64::new(0),
+            docker_uploads: AtomicU64::new(0),
+            npm_downloads: AtomicU64::new(0),
+            maven_downloads: AtomicU64::new(0),
+            maven_uploads: AtomicU64::new(0),
+            cargo_downloads: AtomicU64::new(0),
+            pypi_downloads: AtomicU64::new(0),
+            start_time: Instant::now(),
+        }
+    }
+
+    /// Record a download event for the specified registry
+    pub fn record_download(&self, registry: &str) {
+        self.downloads.fetch_add(1, Ordering::Relaxed);
+        match registry {
+            "docker" => self.docker_downloads.fetch_add(1, Ordering::Relaxed),
+            "npm" => self.npm_downloads.fetch_add(1, Ordering::Relaxed),
+            "maven" => self.maven_downloads.fetch_add(1, Ordering::Relaxed),
+            "cargo" => self.cargo_downloads.fetch_add(1, Ordering::Relaxed),
+            "pypi" => self.pypi_downloads.fetch_add(1, Ordering::Relaxed),
+            _ => 0,
+        };
+    }
+
+    /// Record an upload event for the specified registry
+    pub fn record_upload(&self, registry: &str) {
+        self.uploads.fetch_add(1, Ordering::Relaxed);
+        match registry {
+            "docker" => self.docker_uploads.fetch_add(1, Ordering::Relaxed),
+            "maven" => self.maven_uploads.fetch_add(1, Ordering::Relaxed),
+            _ => 0,
+        };
+    }
+
+    /// Record a cache hit
+    pub fn record_cache_hit(&self) {
+        self.cache_hits.fetch_add(1, Ordering::Relaxed);
+    }
+
+    /// Record a cache miss
+    pub fn record_cache_miss(&self) {
+        self.cache_misses.fetch_add(1, Ordering::Relaxed);
+    }
+
+    /// Calculate the cache hit rate as a percentage
+    pub fn cache_hit_rate(&self) -> f64 {
+        let hits = self.cache_hits.load(Ordering::Relaxed);
+        let misses = self.cache_misses.load(Ordering::Relaxed);
+        let total = hits + misses;
+        if total == 0 {
+            0.0
+        } else {
+            (hits as f64 / total as f64) * 100.0
+        }
+    }
+
+    /// Get download count for a specific registry
+    pub fn get_registry_downloads(&self, registry: &str) -> u64 {
+        match registry {
+            "docker" => self.docker_downloads.load(Ordering::Relaxed),
+            "npm" => self.npm_downloads.load(Ordering::Relaxed),
+            "maven" => self.maven_downloads.load(Ordering::Relaxed),
+            "cargo" => self.cargo_downloads.load(Ordering::Relaxed),
+            "pypi" => self.pypi_downloads.load(Ordering::Relaxed),
+            _ => 0,
+        }
+    }
+
+    /// Get upload count for a specific registry
+    pub fn get_registry_uploads(&self, registry: &str) -> u64 {
+        match registry {
+            "docker" => self.docker_uploads.load(Ordering::Relaxed),
+            "maven" => self.maven_uploads.load(Ordering::Relaxed),
+            _ => 0,
+        }
+    }
+}
+
+impl Default for DashboardMetrics {
+    fn default() -> Self {
+        Self::new()
+    }
+}