Add admin UI + MinIO image uploads

- Admin API: list/edit posts (incl. drafts, raw markdown), moderate comments, subscribers,
  author bio/links, and presigned image upload to MinIO (bucket is public-read for covers).
- Admin UI at /admin: post editor with cover-image upload, comment moderation, subscriber list.
- Public security switched to authenticated-paths so static assets (/images, /data) stay public.

.gitea/ci-settings.xml

@@ -1,26 +0,0 @@
-<?xml version="1.0" encoding="UTF-8"?>
-<settings xmlns="http://maven.apache.org/SETTINGS/1.0.0"
-          xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
-          xsi:schemaLocation="http://maven.apache.org/SETTINGS/1.0.0 http://maven.apache.org/xsd/settings-1.0.0.xsd">
-  <servers>
-    <server>
-      <id>gitea</id>
-      <username>${env.MAVEN_USER}</username>
-      <password>${env.MAVEN_TOKEN}</password>
-    </server>
-  </servers>
-  <profiles>
-    <profile>
-      <id>gitea</id>
-      <repositories>
-        <repository>
-          <id>gitea</id>
-          <url>https://git.thebennett.net/api/packages/austin/maven</url>
-          <releases><enabled>true</enabled></releases>
-          <snapshots><enabled>true</enabled></snapshots>
-        </repository>
-      </repositories>
-    </profile>
-  </profiles>
-  <activeProfiles><activeProfile>gitea</activeProfile></activeProfiles>
-</settings>