docs: address spec review feedback for AdGuard module

- Add complete container definition with security options
- Add SOPS template code with ClientID interpolation
- Fix nginx location to use regex for /dns-query/{clientId}
- Add volume persistence for stats/logs
- Add proxy_http_version for DoH
- Document security considerations

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

docs/superpowers/specs/2026-03-18-adguard-home-design.md

@@ -87,6 +87,11 @@ myModules.adguard = {
 │         │             │  │AdGuardHome. │  ← generated by    │   │
 │         │             │  │   yaml      │    Nix from SOPS   │   │
 │         │             │  └─────────────┘                    │   │
+│         │             │                                      │   │
+│         │             │  ┌─────────────┐                    │   │
+│         │             │  │  data/      │  ← persistent vol  │   │
+│         │             │  │ (stats,logs)│                    │   │
+│         │             │  └─────────────┘                    │   │
 │         │             └─────────────────────────────────────┘   │
 │         │                                                        │
 │         ▼                                                        │
@@ -101,7 +106,8 @@ myModules.adguard = {
 
 ### Request Flow
 
-1. External client sends DoH request to `https://dns.ashisgreat.xyz/dns-query/{clientId}`
+1. External client sends DoH request to `https://dns.ashisgreat.xyz/dns-query/CLIENTID`
+   - Example: `https://dns.ashisgreat.xyz/dns-query/xK9mP2vL7nQ4`
 2. Nginx handles TLS termination and proxies to AdGuard container on `127.0.0.1:3000`
 3. AdGuard validates the ClientID in the request path
 4. Unknown ID → Connection dropped
@@ -132,69 +138,154 @@ myModules.adguard = {
   ];
 };
 
-# SOPS secret declarations
+# SOPS secret declarations (auto-created by module or manual)
 sops.secrets.adguard_client_phone = { };
 sops.secrets.adguard_client_laptop = { };
 ```
 
-### Generated AdGuardHome.yaml
+## Implementation Details
 
-The module generates the config via SOPS template:
+### Container Definition
 
-```yaml
-dns:
-  upstream_dns:
-    - https://dns.mullvad.net/dns-query
-  bootstrap_dns:
-    - 194.242.2.2
-    - 2a07:e340::2
+```nix
+virtualisation.oci-containers.containers."adguard" = {
+  image = "docker.io/adguard/adguardhome:latest";
+  ports = [ "127.0.0.1:${toString cfg.port}:3000/tcp" ];
+  extraOptions = [
+    "--cap-drop=ALL"
+    "--read-only"
+    "--tmpfs=/tmp"
+  ];
+  volumes = [
+    "${config.sops.templates."adguardhome.yaml".path}:/opt/adguardhome/conf/AdGuardHome.yaml:ro"
+    "adguard-data:/opt/adguardhome/work"
+  ];
+};
+```
 
+**Notes:**
+- Container runs with minimal capabilities (`--cap-drop=ALL`)
+- Config file is read-only (managed by Nix/SOPS)
+- `adguard-data` volume persists stats and query logs
+
+### Data Directory
+
+```nix
+systemd.tmpfiles.rules = [
+  "d /var/lib/adguard 0755 root root -"
+];
+```
+
+### SOPS Template for AdGuardHome.yaml
+
+```nix
+sops.templates."adguardhome.yaml" = {
+  content = ''
     http:
       address: 0.0.0.0:3000
 
+    dns:
+      upstream_dns:
+        - ${cfg.upstreamDoh}
+      bootstrap_dns:
+        ${lib.concatStringsSep "\n        " (map (d: "- ${d}") cfg.bootstrapDns)}
+      querylog_enabled: true
+      querylog_file_enabled: true
+      statistics_enabled: true
+
     clients:
       persistent:
-    - name: phone
+        ${lib.concatStringsSep "\n        " (
+          map (client: ''
+            - name: ${client.name}
               ids:
-        - xK9mP2vL7nQ4
-    - name: laptop
-      ids:
-        - jH3fR8wT5yB1
+                - ${config.sops.placeholder.${client.idSecret}}
+          '') cfg.clients
+        )}
+
+    filtering:
+      protection_enabled: true
+      filtering_enabled: true
+
+    safebrowsing:
+      enabled: false
+
+    parental:
+      enabled: false
+
+    safesearch:
+      enabled: false
+
+    log:
+      file: ""
+      max_backups: 0
+      max_size: 100
+      compress: false
+      local_time: false
+      verbose: false
+  '';
+};
+```
+
+### SOPS Secret Declarations (Auto-generated)
+
+The module automatically declares SOPS secrets for each client:
+
+```nix
+sops.secrets = lib.mkMerge (
+  map (client: {
+    ${client.idSecret} = { };
+  }) cfg.clients
+);
 ```
 
 ## Nginx Configuration
 
-The module configures nginx directly (not via the nginx module):
+The module configures nginx directly (not via the nginx module) because DoH requires special handling:
 
 ```nix
-services.nginx.virtualHosts."dns.ashisgreat.xyz" = {
+services.nginx.virtualHosts."${cfg.domain}" = {
   enableACME = true;
   forceSSL = true;
 
-  locations."/dns-query" = {
-    proxyPass = "http://127.0.0.1:3000";
+  # Regex location to match /dns-query and /dns-query/{clientId}
+  locations."~ ^/dns-query" = {
+    proxyPass = "http://127.0.0.1:${toString cfg.port}";
     extraConfig = ''
+      proxy_http_version 1.1;
       proxy_set_header Host $host;
       proxy_set_header X-Real-IP $remote_addr;
       proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
       proxy_set_header X-Forwarded-Proto $scheme;
-      proxy_method POST;
+
+      # DoH uses POST with application/dns-message
       proxy_pass_request_body on;
+      proxy_set_header Content-Type "application/dns-message";
+
+      # Buffer settings for DNS queries
       proxy_buffers 8 16k;
       proxy_buffer_size 32k;
     '';
   };
 
+  # Block all other paths including admin UI
   locations."/" = {
     return = "404";
   };
 };
+
+# Ensure nginx user can access ACME certs
+users.users.nginx.extraGroups = [ "acme" ];
+
+# Open HTTPS port
+networking.firewall.allowedTCPPorts = [ 443 ];
 ```
 
-**Notes:**
-- Admin UI not exposed externally
-- All config changes via git + `nixos-rebuild switch`
-- ACME certificate auto-provisioned
+**Security Notes:**
+- ClientIDs appear in URL paths and may be logged by nginx
+- Consider filtering nginx logs to redact ClientIDs if needed
+- Admin UI is completely blocked (returns 404)
+- No rate limiting configured (can be added if abuse occurs)
 
 ## Firewall