feat: behind-the-scenes 👍/👎 rating system (fine-tune data collection)

Brian can rate Lyra's outputs as he uses her; each rating is stored as a
(context, content, rating) triple — the shape a future fine-tune / preference
dataset wants, collected passively during real use.

- memory: ratings table + add_rating (upsert: one row per item, re-rating
  replaces), list_ratings, rating_counts
- server: POST /rate, GET /ratings/counts, GET /ratings/export (JSONL download)
- chat UI: subtle 👍/👎 on each assistant reply, captures the prompting message
  as context
- journal/reflection UI: 👍/👎 on each thought
- tests: counts + upsert-replace behavior

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

lyra/web/static/journal.html

@@ -52,6 +52,12 @@
     .time { color: var(--fade); font-size: .72rem; }
     .src  { color: var(--fade); font-size: .68rem; opacity: .7; }
     .text { font-size: .98rem; line-height: 1.55; }
+    .jrate { display: flex; gap: 8px; margin-top: 6px; opacity: .35; }
+    .entry:hover .jrate { opacity: .85; }
+    .jr { background: none; border: none; cursor: pointer; font-size: .85rem; padding: 2px 5px;
+          border-radius: 5px; filter: grayscale(.6); -webkit-tap-highlight-color: transparent; }
+    .jr:hover { filter: none; background: rgba(255,122,0,.12); }
+    .jr.rated { filter: none; background: rgba(255,122,0,.25); opacity: 1; }
     .empty { color: var(--fade); text-align: center; padding: 44px 16px; }
     .hidden { display: none !important; }
   </style>
@@ -115,12 +121,29 @@
               ${e.source ? `<span class="src">via ${esc(e.source)}</span>` : ''}
             </div>
             <div class="text">${esc(e.content)}</div>
+            <div class="jrate">
+              <button class="jr" data-id="${e.id}" data-val="1">👍</button>
+              <button class="jr" data-id="${e.id}" data-val="-1">👎</button>
+            </div>
           </div>
         </div>`;
       }
       root.innerHTML = html;
     }
 
+    // 👍/👎 on a thought -> /rate (fine-tune signal)
+    root.addEventListener('click', (ev) => {
+      const b = ev.target.closest('.jr'); if (!b) return;
+      const e = entries.find(x => String(x.id) === b.dataset.id); if (!e) return;
+      fetch('/rate', {
+        method: 'POST', headers: { 'Content-Type': 'application/json' },
+        body: JSON.stringify({ kind: e.kind, rating: Number(b.dataset.val), content: e.content, ref: e.id })
+      }).catch(() => {});
+      const bar = b.parentElement;
+      bar.querySelectorAll('.jr').forEach(x => x.classList.remove('rated'));
+      b.classList.add('rated');
+    });
+
     async function load(){
       try {
         const r = await fetch('/journal/data', { cache: 'no-store' });