Add training tracking: exercises with instructions, one-tap session log, consistency overview

Exercises (name + how-to note) are a new synced collection with the same
LWW/tombstone contract as events, served by POST /api/exercises/sync.
Training sessions are ordinary events (type "training") referencing an
exercise by id, so they ride the existing event sync unchanged.

The Training panel lists each exercise with last-trained / this-week /
streak stats, expandable instructions, and a one-tap Log button with the
usual undo/add-note snackbar. An exercise-by-day heatmap shows the last
14 days of consistency, and history and the daily overview count
training sessions like any other event.

src/style.css

@@ -10,6 +10,7 @@
   --pee: #ffd23f;
   --poo: #8a5a3b;
   --weight: #2bb3a3;
+  --training: #b04ecf;
   --danger: #d64545;
   --gain: #2e9e5b;
   --border: #e9e6f5;
@@ -357,6 +358,7 @@ textarea { resize: vertical; }
 .event[data-type="pee"] .dot { background: var(--pee); }
 .event[data-type="poo"] .dot { background: var(--poo); }
 .event[data-type="weight"] .dot { background: var(--weight); }
+.event[data-type="training"] .dot { background: var(--training); }
 
 .event .time { font-variant-numeric: tabular-nums; color: var(--muted); min-width: 60px; }
 .event .label { font-weight: 600; min-width: 110px; }
@@ -755,6 +757,73 @@ input.switch:checked::after { transform: translateX(18px); }
 .chart-svg .hm-pee { fill: var(--pee); }
 .chart-svg .hm-poo { fill: var(--poo); }
 .chart-svg .hm-eat { fill: var(--eat); }
+.chart-svg .hm-training { fill: var(--training); }
+
+/* ---------- training ---------- */
+.training-list {
+  list-style: none;
+  margin: 0 0 10px;
+  padding: 0;
+  display: flex;
+  flex-direction: column;
+  gap: 8px;
+}
+.training-list:empty { margin: 0; }
+
+.exercise {
+  background: var(--bg);
+  border: 1px solid var(--border);
+  border-radius: var(--radius);
+  padding: 10px 12px;
+}
+
+.ex-row {
+  display: flex;
+  align-items: center;
+  gap: 10px;
+  cursor: pointer;
+}
+
+.ex-main {
+  flex: 1;
+  min-width: 0;
+  display: flex;
+  flex-direction: column;
+  gap: 2px;
+}
+
+.ex-name { font-weight: 600; }
+.ex-meta { color: var(--muted); font-size: 0.8rem; }
+
+button.ex-log {
+  background: var(--training);
+  padding: 8px 14px;
+  flex-shrink: 0;
+}
+
+.ex-detail { display: none; }
+.exercise.expanded .ex-detail {
+  display: flex;
+  align-items: flex-start;
+  gap: 10px;
+  margin-top: 10px;
+  padding-top: 10px;
+  border-top: 1px solid var(--border);
+}
+
+.ex-note {
+  flex: 1;
+  margin: 0;
+  color: var(--muted);
+  font-size: 0.9rem;
+  line-height: 1.4;
+  white-space: pre-wrap;
+}
+
+button.ex-edit { padding: 6px 12px; flex-shrink: 0; }
+
+.training-add { width: 100%; }
+.training-chart { margin-top: 16px; }
 
 /* ---------- collapsible panels ---------- */
 section.collapsible > h2 {