Phase 5: library & stats

- Full library home page: question list with per-user mastery stats,
  search/source filter, sort (A-Z, weakest first, most-seen), source
  breakdown in header, Take a test CTA.
- GET/POST /questions/{id}: view and edit question text, source, answers;
  radio-select correct answer; shows seen×/correct% stat.
- POST /questions/{id}/delete: hard delete (cascades to answers via FK).
- repo: ListQuestions supports SortWeakest/SortMostSeen via LEFT JOIN;
  added CountBySource, UpdateQuestion, UpdateAnswers, DeleteQuestion.
- render: added pct template func (correct*100/seen).

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

internal/handlers/home.go

@@ -1,20 +1,89 @@
 package handlers
 
 import (
+	"log/slog"
 	"net/http"
 
 	"qbank/internal/auth"
+	"qbank/internal/db"
+	"qbank/internal/models"
 )
 
+// QuestionRow pairs a question with its per-user stat for the library display.
+type QuestionRow struct {
+	Q    *models.Question
+	Stat *models.UserQuestionStat // nil = never seen in a test
+}
+
 type HomeHandler struct {
 	auth   *auth.Manager
+	repo   *db.Repo
 	render *Renderer
 }
 
-func NewHomeHandler(a *auth.Manager, r *Renderer) *HomeHandler {
-	return &HomeHandler{auth: a, render: r}
+func NewHomeHandler(a *auth.Manager, repo *db.Repo, r *Renderer) *HomeHandler {
+	return &HomeHandler{auth: a, repo: repo, render: r}
 }
 
 func (h *HomeHandler) Handle(w http.ResponseWriter, r *http.Request) {
-	h.render.Render(w, http.StatusOK, "home", BaseData(h.auth, r))
+	user := auth.UserFromCtx(r.Context())
+
+	sortParam := r.URL.Query().Get("sort")
+	search := r.URL.Query().Get("q")
+	source := r.URL.Query().Get("source")
+
+	var sortOrder db.SortOrder
+	switch sortParam {
+	case "weakest":
+		sortOrder = db.SortWeakest
+	case "seen":
+		sortOrder = db.SortMostSeen
+	default:
+		sortParam = "alpha"
+		sortOrder = db.SortAlpha
+	}
+
+	questions, err := h.repo.ListQuestions(db.ListFilter{
+		Source: source,
+		Search: search,
+		Sort:   sortOrder,
+		UserID: user.ID,
+	})
+	if err != nil {
+		slog.Error("list questions", "err", err)
+		HTTPError(w, http.StatusInternalServerError)
+		return
+	}
+
+	ids := make([]string, len(questions))
+	for i, q := range questions {
+		ids[i] = q.ID
+	}
+
+	stats, err := h.repo.GetStatsForUser(user.ID, ids)
+	if err != nil {
+		slog.Error("get stats", "err", err)
+		HTTPError(w, http.StatusInternalServerError)
+		return
+	}
+
+	rows := make([]QuestionRow, len(questions))
+	for i, q := range questions {
+		rows[i] = QuestionRow{Q: q, Stat: stats[q.ID]}
+	}
+
+	totalQ, _ := h.repo.CountQuestions()
+	totalA, _ := h.repo.CountAnswers()
+	sourceCounts, _ := h.repo.CountBySource()
+
+	data := BaseData(h.auth, r)
+	data["Questions"] = rows
+	data["TotalQ"] = totalQ
+	data["TotalA"] = totalA
+	data["SourceStats"] = sourceCounts
+	data["Sort"] = sortParam
+	data["Search"] = search
+	data["SelectedSource"] = source
+
+	h.render.Render(w, http.StatusOK, "home", data)
 }