Add Navidrome and system services modules

Configure Navidrome settings (MusicFolder, Port 4533, Address 0.0.0.0),
open firewall and create tmpfiles entry for the music directory.

Enable system services: weekly fstrim, zram swap (zstd), Avahi mDNS,
psd,
fwupd, earlyoom and plocate

modules/services.nix

@@ -0,0 +1,81 @@
+# modules/services.nix
+# System services: SSD maintenance, swap, mDNS, profile sync
+{ config, pkgs, lib, ... }:
+
+{
+  # ═══════════════════════════════════════════════════════════════
+  # SSD MAINTENANCE
+  # ═══════════════════════════════════════════════════════════════
+  # Weekly TRIM for SSDs (improves longevity and performance)
+  services.fstrim = {
+    enable = true;
+    interval = "weekly";
+  };
+
+  # ═══════════════════════════════════════════════════════════════
+  # ZRAM SWAP
+  # ═══════════════════════════════════════════════════════════════
+  # Compressed swap in RAM - better than no swap, faster than disk
+  zramSwap = {
+    enable = true;
+    algorithm = "zstd";        # Best compression ratio
+    memoryPercent = 50;        # Use up to 50% of RAM for compressed swap
+  };
+
+  # ═══════════════════════════════════════════════════════════════
+  # MDNS / AVAHI
+  # ═══════════════════════════════════════════════════════════════
+  # mDNS for local network discovery (.local domains)
+  services.avahi = {
+    enable = true;
+    nssmdns4 = true;           # Enable .local resolution
+    openFirewall = true;       # Allow mDNS through firewall
+    
+    publish = {
+      enable = true;
+      addresses = true;
+      workstation = true;
+    };
+  };
+
+  # ═══════════════════════════════════════════════════════════════
+  # PROFILE SYNC DAEMON
+  # ═══════════════════════════════════════════════════════════════
+  # Sync browser profiles to RAM for faster performance
+  # Works with Firefox/Zen Browser profiles
+  services.psd = {
+    enable = true;
+  };
+
+  # User needs to configure ~/.config/psd/psd.conf after first run
+  # Default will auto-detect Firefox profiles
+
+  # ═══════════════════════════════════════════════════════════════
+  # ADDITIONAL SYSTEM OPTIMIZATIONS
+  # ═══════════════════════════════════════════════════════════════
+  
+  # Enable firmware updates
+  services.fwupd.enable = true;
+
+  # Thermald for Intel CPUs (AMD uses different thermal management)
+  # Uncomment if on Intel:
+  # services.thermald.enable = true;
+
+  # Early OOM killer - prevents system freeze on memory exhaustion
+  services.earlyoom = {
+    enable = true;
+    freeMemThreshold = 5;      # Start killing at 5% free memory
+    freeSwapThreshold = 10;    # Also consider swap
+    enableNotifications = true;
+  };
+
+  # ═══════════════════════════════════════════════════════════════
+  # LOCATE DATABASE
+  # ═══════════════════════════════════════════════════════════════
+  # Fast file search with plocate
+  services.locate = {
+    enable = true;
+    package = pkgs.plocate;
+    interval = "daily";
+  };
+}