docs: update README, Obsidian docs, and gap backlog after test optimization

- Update test count: 286/288 passing (was 222/224)
- Document TestMain per-package architecture
- Document TruncateTables optimization (~60% faster)
- Add local-dev-2.sh tee streaming for real-time test output
- Fix flaky admin reserve walk-in tests (time.Now → noon tomorrow)
- Add gap backlog item #51 for completed test optimization work

backend/handlers/bookings/admin_reserve_test.go

@@ -69,7 +69,8 @@ func TestAdminReserveSlot_WalkIn_Success(t *testing.T) {
 	}
 	defer fixtures.DeleteUser(db.DB, adminID)
 
-	now := time.Now()
+	tomorrow := time.Now().Add(24 * time.Hour)
+	now := time.Date(tomorrow.Year(), tomorrow.Month(), tomorrow.Day(), 12, 0, 0, 0, tomorrow.Location())
 	req := AdminReserveSlotRequest{
 		ReservationType: "walkin",
 		StartTime:       now,
@@ -390,7 +391,8 @@ func TestAdminReserveSlot_ReplacesExisting(t *testing.T) {
 	}
 	defer fixtures.DeleteUser(db.DB, adminID)
 
-	now := time.Now()
+	tomorrow := time.Now().Add(24 * time.Hour)
+	now := time.Date(tomorrow.Year(), tomorrow.Month(), tomorrow.Day(), 12, 0, 0, 0, tomorrow.Location())
 
 	req := AdminReserveSlotRequest{
 		ReservationType: "walkin",
@@ -399,6 +401,7 @@ func TestAdminReserveSlot_ReplacesExisting(t *testing.T) {
 		TTLMinutes:      15,
 	}
 
+	// First reservation
 	handler := http.HandlerFunc(AdminReserveSlotHandler)
 	w := makeAdminReserveRequest(handler, req, adminID)