README: center stat strip and use meaningful icons instead of decoration

Table wasn't centered on the page (only text inside cells was) - added
align=\"center\" to the table itself. Icons were arbitrary; replaced
with ones that actually trace back to the related system's own icon
elsewhere in this doc (Docker whale for compose stacks, the brick wall
from Firewall & Network Segmentation for trust boundaries, the same
cycle icon Orchestration uses for automated maintenance flows).

README.md

@@ -10,13 +10,13 @@
 [![YouTube](https://img.shields.io/badge/YouTube-red?style=for-the-badge&logo=youtube&logoColor=white)](https://www.youtube.com/@nomadianation)
 -->
 
-<table>
+<table align="center">
 <tr>
-<td align="center"><strong>11</strong><br/>fleet hosts</td>
+<td align="center">🖥️<br/><strong style="font-size:1.6em;">11</strong><br/>fleet hosts</td>
-<td align="center"><strong>53</strong><br/>compose stacks</td>
+<td align="center">🐳<br/><strong style="font-size:1.6em;">53</strong><br/>compose stacks</td>
-<td align="center"><strong>15</strong><br/>documented systems</td>
+<td align="center">📚<br/><strong style="font-size:1.6em;">15</strong><br/>documented systems</td>
-<td align="center"><strong>4</strong><br/>trust boundaries</td>
+<td align="center">🧱<br/><strong style="font-size:1.6em;">4</strong><br/>trust boundaries</td>
-<td align="center"><strong>13</strong><br/>automated maintenance flows</td>
+<td align="center">🔁<br/><strong style="font-size:1.6em;">13</strong><br/>automated maintenance flows</td>
 </tr>
 </table>