Add server-wide and user-only federation controls (#133)

### Description

Completes #122

### Please confirm

- [x] I am the legal owner or represent the legal owner of all work submitted (including LLM-generated code, if any)
- [x] I consent to my changes being added to this FOSS project
- [x] I have confirmed that this does not add new errors or warnings with `utils/clippy.sh`
- [ ] This PR used LLMs to generate some or all of the code changes

Reviewed-on: https://git.ngram.ca/OpenJam/rc-servers/pulls/133

assets/templates/rc_society/dashboard.html.hbs

@@ -200,10 +200,18 @@
       <div class="access-box">
         <h4 class="access-box-title">Federation</h4>
         <div class="box-details">
-          <div class="box-details-key">TODO</div> <!-- TODO -->
-          <div class="box-details-value">TODO</div>
+          <div class="box-details-key">Enabled</div>
+          <div class="box-details-value">{{form.fediverse.enabled}}</div>
+          <div class="box-details-key">Blocked</div>
+          <div class="box-details-value">
+            {{#each form.fediverse.defederated}}
+              <span>{{this}}</span><br/>
+            {{else}}
+              <span>[None]</span>
+            {{/each}}
+          </div>
         </div>
-        <a href="#"> <!-- TODO -->
+        <a href="/federation/list"> <!-- TODO -->
           <div class="access-box-banner">
             Manage My Federation
           </div>