feat: add Halo version variable to theme model (#6677)

#### What type of PR is this?
/kind feature
/milestone 2.20.x
/area theme

#### What this PR does / why we need it:
主题支持通过 `${site.version}` 得到 Halo 版本号

#### Which issue(s) this PR fixes:
Fixes #6676

#### Does this PR introduce a user-facing change?
```release-note
主题支持通过 `${site.version}` 得到 Halo 版本号
```

application/src/main/java/run/halo/app/theme/SiteSettingVariablesAcquirer.java

@@ -7,6 +7,7 @@ import org.springframework.web.server.ServerWebExchange;
 import reactor.core.publisher.Mono;
 import run.halo.app.infra.ExternalUrlSupplier;
 import run.halo.app.infra.SystemConfigurableEnvironmentFetcher;
+import run.halo.app.infra.SystemVersionSupplier;
 import run.halo.app.theme.finders.vo.SiteSettingVo;
 
 /**
@@ -21,6 +22,7 @@ public class SiteSettingVariablesAcquirer implements ViewContextBasedVariablesAc
 
     private final SystemConfigurableEnvironmentFetcher environmentFetcher;
     private final ExternalUrlSupplier externalUrlSupplier;
+    private final SystemVersionSupplier systemVersionSupplier;
 
     @Override
     public Mono<Map<String, Object>> acquire(ServerWebExchange exchange) {
@@ -28,7 +30,8 @@ public class SiteSettingVariablesAcquirer implements ViewContextBasedVariablesAc
             .filter(configMap -> configMap.getData() != null)
             .map(configMap -> {
                 SiteSettingVo siteSettingVo = SiteSettingVo.from(configMap)
-                    .withUrl(externalUrlSupplier.getURL(exchange.getRequest()));
+                    .withUrl(externalUrlSupplier.getURL(exchange.getRequest()))
+                    .withVersion(systemVersionSupplier.get().toString());
                 return Map.of("site", siteSettingVo);
             });
     }

application/src/main/java/run/halo/app/theme/finders/vo/SiteSettingVo.java

@@ -25,6 +25,9 @@ public class SiteSettingVo {
     @With
     URL url;
 
+    @With
+    String version;
+
     String subtitle;
 
     String logo;

application/src/test/java/run/halo/app/theme/SiteSettingVariablesAcquirerTest.java

@@ -6,6 +6,7 @@ import static org.mockito.Mockito.mock;
 import static org.mockito.Mockito.verify;
 import static org.mockito.Mockito.when;
 
+import com.github.zafarkhaja.semver.Version;
 import java.net.MalformedURLException;
 import java.net.URL;
 import java.util.Map;
@@ -20,6 +21,7 @@ import reactor.test.StepVerifier;
 import run.halo.app.extension.ConfigMap;
 import run.halo.app.infra.ExternalUrlSupplier;
 import run.halo.app.infra.SystemConfigurableEnvironmentFetcher;
+import run.halo.app.infra.SystemVersionSupplier;
 import run.halo.app.theme.finders.vo.SiteSettingVo;
 
 /**
@@ -32,6 +34,10 @@ import run.halo.app.theme.finders.vo.SiteSettingVo;
 public class SiteSettingVariablesAcquirerTest {
     @Mock
     private ExternalUrlSupplier externalUrlSupplier;
+
+    @Mock
+    private SystemVersionSupplier systemVersionSupplier;
+
     @Mock
     private SystemConfigurableEnvironmentFetcher environmentFetcher;
 
@@ -45,6 +51,7 @@ public class SiteSettingVariablesAcquirerTest {
 
         var url = new URL("https://halo.run");
         when(externalUrlSupplier.getURL(any())).thenReturn(url);
+        when(systemVersionSupplier.get()).thenReturn(Version.parse("0.0.0-alpha.1"));
         when(environmentFetcher.getConfigMap()).thenReturn(Mono.just(configMap));
 
         siteSettingVariablesAcquirer.acquire(mock(ServerWebExchange.class))
@@ -52,9 +59,13 @@ public class SiteSettingVariablesAcquirerTest {
             .consumeNextWith(result -> {
                 assertThat(result).containsKey("site");
                 assertThat(result.get("site")).isInstanceOf(SiteSettingVo.class);
-                assertThat((SiteSettingVo) result.get("site"))
+                var site = (SiteSettingVo) result.get("site");
+                assertThat(site)
                     .extracting(SiteSettingVo::getUrl)
                     .isEqualTo(url);
+                assertThat(site)
+                    .extracting(SiteSettingVo::getVersion)
+                    .isEqualTo("0.0.0-alpha.1");
             })
             .verifyComplete();
         verify(externalUrlSupplier).getURL(any());