feat: hide entry content from list, add GET /api/entries/:id/content endpoint

Content is no longer returned in the entries list. A separate endpoint
returns plain text content for clipboard copying on demand.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

frontend/src/App.css

@@ -0,0 +1,92 @@
+.app {
+  max-width: 800px;
+  margin: 0 auto;
+  padding: 2rem;
+  font-family: system-ui, -apple-system, sans-serif;
+}
+
+h1 {
+  margin-bottom: 1.5rem;
+}
+
+.create-section {
+  display: flex;
+  flex-direction: column;
+  gap: 0.5rem;
+  margin-bottom: 2rem;
+}
+
+.create-section textarea {
+  width: 100%;
+  padding: 0.75rem;
+  font-size: 1rem;
+  border: 1px solid #ccc;
+  border-radius: 4px;
+  resize: vertical;
+  font-family: inherit;
+  box-sizing: border-box;
+}
+
+.create-section button {
+  align-self: flex-end;
+  padding: 0.5rem 1.5rem;
+  font-size: 1rem;
+  cursor: pointer;
+  background: #333;
+  color: white;
+  border: none;
+  border-radius: 4px;
+}
+
+.create-section button:hover {
+  background: #555;
+}
+
+.entries-list {
+  display: flex;
+  flex-direction: column;
+  gap: 1rem;
+}
+
+.entry {
+  border: 1px solid #ddd;
+  border-radius: 4px;
+  padding: 1rem;
+}
+
+.entry-content {
+  margin: 0 0 0.75rem 0;
+  white-space: pre-wrap;
+  word-wrap: break-word;
+  font-family: inherit;
+  font-size: 1rem;
+}
+
+.entry-meta {
+  display: flex;
+  justify-content: space-between;
+  align-items: center;
+}
+
+.entry-date {
+  color: #888;
+  font-size: 0.85rem;
+}
+
+.entry-actions {
+  display: flex;
+  gap: 0.5rem;
+}
+
+.entry-actions button {
+  padding: 0.25rem 0.75rem;
+  font-size: 0.85rem;
+  cursor: pointer;
+  border: 1px solid #ccc;
+  border-radius: 4px;
+  background: white;
+}
+
+.entry-actions button:hover {
+  background: #f0f0f0;
+}