feat(sdk): AuthConfigs, JSON Schema, examples, and release checksum CI

Add craftlabs-auth-config.schema.json, Java AuthConfigs model with tests,
example configs aligned to BP-10, C/Java/auth-config documentation,
native header notes, RELEASING guide, and workflow to verify SDK
artifact checksums on release tags.

Made-with: Cursor

java/pom.xml

@@ -21,6 +21,10 @@
         <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
         <maven.compiler.release>17</maven.compiler.release>
         <junit.version>5.10.2</junit.version>
+        <jackson.version>2.17.2</jackson.version>
+        <json-schema-validator.version>1.5.7</json-schema-validator.version>
+        <!-- 默认跳过 GPG；发布签名：mvn -Prelease-sign verify（见 RELEASING.md） -->
+        <gpg.skip>true</gpg.skip>
     </properties>
 
     <dependencyManagement>
@@ -36,6 +40,17 @@
                 <version>${junit.version}</version>
                 <scope>test</scope>
             </dependency>
+            <dependency>
+                <groupId>com.fasterxml.jackson.core</groupId>
+                <artifactId>jackson-databind</artifactId>
+                <version>${jackson.version}</version>
+            </dependency>
+            <dependency>
+                <groupId>com.networknt</groupId>
+                <artifactId>json-schema-validator</artifactId>
+                <version>${json-schema-validator.version}</version>
+                <scope>test</scope>
+            </dependency>
         </dependencies>
     </dependencyManagement>
 
@@ -52,7 +67,39 @@
                     <artifactId>maven-surefire-plugin</artifactId>
                     <version>3.2.5</version>
                 </plugin>
+                <plugin>
+                    <groupId>org.apache.maven.plugins</groupId>
+                    <artifactId>maven-gpg-plugin</artifactId>
+                    <version>3.2.7</version>
+                </plugin>
             </plugins>
         </pluginManagement>
     </build>
+
+    <!-- 对发布 JAR 做 GPG 分离签名（.asc）；显式 -Prelease-sign 时启用 -->
+    <profiles>
+        <profile>
+            <id>release-sign</id>
+            <properties>
+                <gpg.skip>false</gpg.skip>
+            </properties>
+            <build>
+                <plugins>
+                    <plugin>
+                        <groupId>org.apache.maven.plugins</groupId>
+                        <artifactId>maven-gpg-plugin</artifactId>
+                        <executions>
+                            <execution>
+                                <id>sign-release-artifacts</id>
+                                <phase>verify</phase>
+                                <goals>
+                                    <goal>sign</goal>
+                                </goals>
+                            </execution>
+                        </executions>
+                    </plugin>
+                </plugins>
+            </build>
+        </profile>
+    </profiles>
 </project>