fix: replace example placeholders with generic guidance

Protocol form:
- Title: 'Round Robin Check-In' → 'Name of the protocol'
- Source: 'Group Works Deck (or @username)' → 'Where it comes from (or @username)'

Collection form:
- Title: 'Protocols for Mutual Aid Groups' → 'Name of the collection'
- Source: 'Author or community (or @username)' → 'Where it comes from (or @username)'

Registration form:
- Display Name: 'Jane Doe' → 'Your name'

frontend/index.html

@@ -114,7 +114,7 @@
     <form id="protocolForm" onsubmit="saveProtocol(event)">
       <div class="form-group">
         <label>Title</label>
-        <input type="text" name="title" required maxlength="255" placeholder="Round Robin Check-In">
+        <input type="text" name="title" required maxlength="255" placeholder="Name of the protocol">
       </div>
       <div class="form-group">
         <label>Description</label>
@@ -130,7 +130,7 @@
       </div>
       <div class="form-group">
         <label>Source</label>
-        <input type="text" name="source" placeholder="Group Works Deck (or @username)">
+        <input type="text" name="source" placeholder="Where it comes from (or @username)">
       </div>
       <div class="form-group">
         <label>Source URL</label>
@@ -180,7 +180,7 @@
     <form id="collectionForm" onsubmit="saveCollection(event)">
       <div class="form-group">
         <label>Title</label>
-        <input type="text" name="coll-title" required maxlength="255" placeholder="Protocols for Mutual Aid Groups">
+        <input type="text" name="coll-title" required maxlength="255" placeholder="Name of the collection">
       </div>
       <div class="form-group">
         <label>Description</label>
@@ -188,7 +188,7 @@
       </div>
       <div class="form-group">
         <label>Source</label>
-        <input type="text" name="coll-source" placeholder="Author or community (or @username)">
+        <input type="text" name="coll-source" placeholder="Where it comes from (or @username)">
       </div>
       <div class="form-group">
         <label>Visibility</label>
@@ -231,7 +231,7 @@
           </div>
           <div class="form-group" id="displayNameGroup">
             <label>Display Name (optional)</label>
-            <input type="text" id="authDisplayName" placeholder="Jane Doe">
+            <input type="text" id="authDisplayName" placeholder="Your name">
           </div>
         </div>
         <div class="actions">