feat: add Phase 4 Logging & Tracking — inline set logging, history views

Add workout logging so users can track sets, reps, weight, and a
"felt easy?" toggle inline from the workout day view via HTMX.
Sessions auto-create on first log. History page shows past sessions
with detailed per-exercise breakdowns.

New services: WorkoutSessionService, LogService
New routes: POST /log, /log/{id}/edit, /log/{id}/delete, GET /history, /history/{id}
New templates: log_form, log_entry, session_card, log_history, session_detail
Modified: exercise_card (inline logging), nav (History link), workouts route (session context)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

app/templates/partials/session_card.html

@@ -0,0 +1,16 @@
+<article>
+    <header>
+        <hgroup>
+            <h3>{{ day.name if day else "Unknown" }} Day</h3>
+            <p>{{ ws.date.strftime('%A, %B %d, %Y') }}</p>
+        </hgroup>
+    </header>
+    {% if ws.notes %}
+    <p>{{ ws.notes }}</p>
+    {% endif %}
+    <footer>
+        <a href="/history/{{ ws.id }}" role="button" class="outline">
+            View Details
+        </a>
+    </footer>
+</article>