Initial commit: smartrun MVP

Garmin run classification and progression tracker. Go backend (MCP
client to mcp-garmin, SQLite store, deterministic rule engine, REST
API) and React/TS frontend (Dashboard, Review Queue, Workout Kinds).

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

backend/internal/api/activities.go

@@ -0,0 +1,67 @@
+package api
+
+import (
+	"net/http"
+	"strconv"
+
+	"github.com/go-chi/chi/v5"
+
+	"smartrun/backend/internal/store"
+)
+
+func (s *Server) handleListActivities(w http.ResponseWriter, r *http.Request) {
+	q := r.URL.Query()
+	filter := store.ActivityFilter{
+		FromDate: q.Get("from"),
+		ToDate:   q.Get("to"),
+	}
+	if limit, err := strconv.Atoi(q.Get("limit")); err == nil {
+		filter.Limit = limit
+	}
+	if offset, err := strconv.Atoi(q.Get("offset")); err == nil {
+		filter.Offset = offset
+	}
+
+	activities, err := s.DB.ListActivities(r.Context(), filter)
+	if err != nil {
+		writeError(w, http.StatusInternalServerError, err.Error())
+		return
+	}
+	writeJSON(w, http.StatusOK, activities)
+}
+
+func (s *Server) handleGetActivity(w http.ResponseWriter, r *http.Request) {
+	id, err := strconv.ParseInt(chi.URLParam(r, "id"), 10, 64)
+	if err != nil {
+		writeError(w, http.StatusBadRequest, "invalid activity id")
+		return
+	}
+
+	activity, ok, err := s.DB.GetActivity(r.Context(), id)
+	if err != nil {
+		writeError(w, http.StatusInternalServerError, err.Error())
+		return
+	}
+	if !ok {
+		writeError(w, http.StatusNotFound, "activity not found")
+		return
+	}
+
+	laps, err := s.DB.LapsForActivity(r.Context(), id)
+	if err != nil {
+		writeError(w, http.StatusInternalServerError, err.Error())
+		return
+	}
+
+	assignment, hasAssignment, err := s.DB.CurrentAssignment(r.Context(), id)
+	if err != nil {
+		writeError(w, http.StatusInternalServerError, err.Error())
+		return
+	}
+
+	resp := map[string]any{"activity": activity, "laps": laps}
+	if hasAssignment {
+		resp["assignment"] = assignment
+	}
+	writeJSON(w, http.StatusOK, resp)
+}