examples: Add CoreDNS for *.local domain resolution (#155)

* examples: Add CoreDNS for *.local domain resolution

Adds a CoreDNS example that resolves *.local to the Traefik host,
making the .local routes in all examples work out of the box.

Also removes the redundant Multi-Container Stacks section from
README since paperless-ngx already demonstrates this pattern.

* examples: Add coredns .env file

examples/README.md

@@ -7,6 +7,7 @@ Real-world examples demonstrating compose-farm patterns for multi-host Docker de
 | Stack | Type | Demonstrates |
 |---------|------|--------------|
 | [traefik](traefik/) | Infrastructure | Reverse proxy, Let's Encrypt, file-provider |
+| [coredns](coredns/) | Infrastructure | Wildcard DNS for `*.local` domains |
 | [mealie](mealie/) | Single container | Traefik labels, resource limits, environment vars |
 | [uptime-kuma](uptime-kuma/) | Single container | Docker socket, user mapping, custom DNS |
 | [paperless-ngx](paperless-ngx/) | Multi-container | Redis + PostgreSQL + App stack |
@@ -53,7 +54,8 @@ labels:
   - traefik.http.routers.myapp-local.entrypoints=web
 ```
 
-> **Note:** `.local` domains require local DNS (e.g., Pi-hole, Technitium) to resolve to your Traefik host.
+> **Note:** `.local` domains require local DNS to resolve to your Traefik host.
+> The [coredns](coredns/) example provides this - edit `Corefile` to set your Traefik IP.
 
 ### Environment Variables
 
@@ -88,22 +90,6 @@ stacks:
   autokuma: all  # Runs on every configured host
 ```
 
-### Multi-Container Stacks
-
-Database-backed apps with multiple services:
-
-```yaml
-services:
-  redis:
-    image: redis:7
-  db:
-    image: postgres:16
-  app:
-    depends_on:
-      - redis
-      - db
-```
-
 ### AutoKuma Labels (Optional)
 
 The autokuma example demonstrates compose-farm's **multi-host feature** - running the same stack on all hosts using the `all` keyword. AutoKuma itself is not part of compose-farm; it's just a good example because it needs to run on every host to monitor local Docker containers.
@@ -124,8 +110,8 @@ cd examples
 # 1. Create the shared network on all hosts
 compose-farm init-network
 
-# 2. Start Traefik first (the reverse proxy)
-compose-farm up traefik
+# 2. Start infrastructure (reverse proxy + DNS)
+compose-farm up traefik coredns
 
 # 3. Start other stacks
 compose-farm up mealie uptime-kuma

examples/compose-farm-state.yaml

@@ -3,6 +3,7 @@ deployed:
   - primary
   - secondary
   - local
+  coredns: primary
   mealie: secondary
   paperless-ngx: primary
   traefik: primary

examples/compose-farm.yaml

@@ -27,6 +27,7 @@ hosts:
 stacks:
   # Infrastructure (runs on primary where Traefik is)
   traefik: primary
+  coredns: primary  # DNS for *.local resolution
 
   # Multi-host stacks (runs on ALL hosts)
   # AutoKuma monitors Docker containers on each host

examples/coredns/.env

@@ -0,0 +1,2 @@
+# CoreDNS doesn't need environment variables
+# The Traefik IP is configured in the Corefile

examples/coredns/Corefile

@@ -0,0 +1,22 @@
+# CoreDNS configuration for .local domain resolution
+#
+# Resolves *.local to the Traefik host IP (where your reverse proxy runs).
+# All other queries are forwarded to upstream DNS.
+
+# Handle .local domains - resolve everything to Traefik's host
+local {
+    template IN A {
+        answer "{{ .Name }} 60 IN A 192.168.1.10"
+    }
+    template IN AAAA {
+        # Return empty for AAAA to avoid delays on IPv4-only networks
+        rcode NOERROR
+    }
+}
+
+# Forward everything else to upstream DNS
+. {
+    forward . 1.1.1.1 8.8.8.8
+    cache 300
+    errors
+}

examples/coredns/compose.yaml

@@ -0,0 +1,27 @@
+# CoreDNS - DNS server for .local domain resolution
+#
+# Demonstrates:
+# - Wildcard DNS for *.local domains
+# - Config file mounting from stack directory
+# - UDP/TCP port exposure
+#
+# This enables all the .local routes in the examples to work.
+# Point your devices/router DNS to this server's IP.
+name: coredns
+services:
+  coredns:
+    image: coredns/coredns:latest
+    container_name: coredns
+    restart: unless-stopped
+    networks:
+      - mynetwork
+    ports:
+      - "53:53/udp"
+      - "53:53/tcp"
+    volumes:
+      - ./Corefile:/root/Corefile:ro
+    command: -conf /root/Corefile
+
+networks:
+  mynetwork:
+    external: true