Fix worker removal and improve web UI defaults

- Parse optional http:// scheme prefix on worker specs so a scheme-typed
  IP is stored cleanly and its remove button works.
- Delete workers by their stored DB host/port instead of re-parsing the
  rendered URL, and surface add/remove errors in the UI.
- Default new builds to git URL instead of zip upload.
- Show worker hostname/IP from agent status in the address column.
- Always include DB host/port in worker API output.

ctrl/static/index.html

@@ -19,6 +19,7 @@
         <input type="text" id="worker-spec" placeholder="host:port (e.g. 192.168.1.40:9001)">
         <button type="submit">Add worker</button>
       </form>
+      <p id="worker-msg" class="msg"></p>
       <div id="workers"></div>
     </section>
 
@@ -28,18 +29,18 @@
         <div class="field">
           <label for="mode">Source</label>
           <select id="mode">
-            <option value="upload">Upload zip</option>
             <option value="git">Git repo</option>
+            <option value="upload">Upload zip</option>
           </select>
         </div>
-        <div class="field" id="upload-field">
-          <label for="file">Project zip</label>
-          <input type="file" id="file" accept=".zip">
-        </div>
-        <div class="field" id="url-field" hidden>
+        <div class="field" id="url-field">
           <label for="url">Git URL</label>
           <input type="text" id="url" placeholder="https://…">
         </div>
+        <div class="field" id="upload-field" hidden>
+          <label for="file">Project zip</label>
+          <input type="file" id="file" accept=".zip">
+        </div>
         <div class="fields-row">
           <div class="field">
             <label for="os">OS</label>