Fix Watchtower crash-loop on newer Docker engines: add DOCKER_API_VERSION=1.44

Watchtower 1.7.1's embedded Docker client negotiates API version 1.25, which
newer Docker daemons (TrueNAS SCALE, Docker Desktop 4.x+) reject with:

  "client version 1.25 is too old. Minimum supported API version is 1.44"

This causes Watchtower to crash-loop immediately on startup, meaning auto-updates
never run. Setting DOCKER_API_VERSION=1.44 as an environment variable forces the
client to negotiate at the correct version.

Added the env var to both compose examples in the README (the generic compose
block and the TrueNAS-specific block), plus an explanatory note so users know
why it's there if they encounter the error.

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

Author: AlpineArchitecture

README.md

@@ -55,12 +55,16 @@ services:
   watchtower:
     image: containrrr/watchtower
     container_name: watchtower
+    environment:
+      - DOCKER_API_VERSION=1.44
     volumes:
       - /var/run/docker.sock:/var/run/docker.sock
     command: --interval 300 programmarr
     restart: unless-stopped
 ```
 
+> **Note:** The `DOCKER_API_VERSION=1.44` env var is required on newer Docker engines (TrueNAS, Docker Desktop 4.x+). Without it, Watchtower crash-loops with "client version 1.25 is too old".
+
 Or update manually any time:
 
 ```bash
@@ -85,6 +89,8 @@ services:
   watchtower:
     image: containrrr/watchtower
     container_name: watchtower
+    environment:
+      - DOCKER_API_VERSION=1.44
     volumes:
       - /var/run/docker.sock:/var/run/docker.sock
     command: --interval 300 programmarr