test(#1188): red — /api/packets must return observer_iata per row

Adds three tests asserting the API surfaces observer_iata on:
- ungrouped /api/packets rows
- grouped /api/packets?groupByHash=true rows
- per-observation entries in /api/packets/{id} detail response

Currently fails: the SQL joins select obs.id, obs.name but not obs.iata.
Fixing the join in cmd/server/db.go is the green commit.

cmd/server/packets_observer_iata_test.go

@@ -0,0 +1,121 @@
+// Test (#1188): /api/packets response must include observer_iata per packet
+// so the frontend can render the IATA inline without per-row observer lookups.
+package main
+
+import (
+	"encoding/json"
+	"net/http/httptest"
+	"testing"
+)
+
+// TestPacketsEndpointIncludesObserverIATA asserts the ungrouped packets endpoint
+// surfaces the joined observer's IATA on each packet row.
+func TestPacketsEndpointIncludesObserverIATA(t *testing.T) {
+	_, router := setupTestServer(t)
+	req := httptest.NewRequest("GET", "/api/packets?limit=10", nil)
+	w := httptest.NewRecorder()
+	router.ServeHTTP(w, req)
+
+	if w.Code != 200 {
+		t.Fatalf("expected 200, got %d", w.Code)
+	}
+	var body map[string]interface{}
+	if err := json.Unmarshal(w.Body.Bytes(), &body); err != nil {
+		t.Fatalf("invalid JSON: %v", err)
+	}
+	packets, ok := body["packets"].([]interface{})
+	if !ok || len(packets) == 0 {
+		t.Fatal("expected non-empty packets array")
+	}
+
+	// Seeded observers: obs1 → SJC, obs2 → SFO. At least one packet row
+	// must carry a non-empty observer_iata string.
+	gotIATA := false
+	for _, p := range packets {
+		m, _ := p.(map[string]interface{})
+		if m == nil {
+			continue
+		}
+		if _, present := m["observer_iata"]; !present {
+			t.Fatalf("packet missing observer_iata field; got keys: %v", keysOfMap(m))
+		}
+		if s, _ := m["observer_iata"].(string); s != "" {
+			gotIATA = true
+		}
+	}
+	if !gotIATA {
+		t.Fatalf("expected at least one packet with non-empty observer_iata (seed has SJC/SFO)")
+	}
+}
+
+// TestPacketsGroupedIncludesObserverIATA asserts the grouped (groupByHash)
+// view also surfaces observer_iata for the header row.
+func TestPacketsGroupedIncludesObserverIATA(t *testing.T) {
+	_, router := setupTestServer(t)
+	req := httptest.NewRequest("GET", "/api/packets?groupByHash=true&limit=10", nil)
+	w := httptest.NewRecorder()
+	router.ServeHTTP(w, req)
+
+	if w.Code != 200 {
+		t.Fatalf("expected 200, got %d", w.Code)
+	}
+	var body map[string]interface{}
+	json.Unmarshal(w.Body.Bytes(), &body)
+	packets, _ := body["packets"].([]interface{})
+	if len(packets) == 0 {
+		t.Fatal("expected non-empty grouped packets")
+	}
+	gotIATA := false
+	for _, p := range packets {
+		m, _ := p.(map[string]interface{})
+		if _, present := m["observer_iata"]; !present {
+			t.Fatalf("grouped packet missing observer_iata field; got keys: %v", keysOfMap(m))
+		}
+		if s, _ := m["observer_iata"].(string); s != "" {
+			gotIATA = true
+		}
+	}
+	if !gotIATA {
+		t.Fatalf("expected at least one grouped packet with non-empty observer_iata")
+	}
+}
+
+// TestPacketDetailObservationsIncludeIATA asserts /api/packets/{id} returns
+// per-observation observer_iata so the detail pane can render it.
+func TestPacketDetailObservationsIncludeIATA(t *testing.T) {
+	_, router := setupTestServer(t)
+	// transmission_id 1 has two observations (obs1 SJC, obs2 SFO) from seedTestData
+	req := httptest.NewRequest("GET", "/api/packets/1", nil)
+	w := httptest.NewRecorder()
+	router.ServeHTTP(w, req)
+	if w.Code != 200 {
+		t.Fatalf("expected 200, got %d: %s", w.Code, w.Body.String())
+	}
+	var body map[string]interface{}
+	json.Unmarshal(w.Body.Bytes(), &body)
+	obs, _ := body["observations"].([]interface{})
+	if len(obs) == 0 {
+		t.Fatalf("expected observations in detail response; body: %s", w.Body.String())
+	}
+	gotIATA := false
+	for _, o := range obs {
+		m, _ := o.(map[string]interface{})
+		if _, present := m["observer_iata"]; !present {
+			t.Fatalf("observation missing observer_iata field; got keys: %v", keysOfMap(m))
+		}
+		if s, _ := m["observer_iata"].(string); s != "" {
+			gotIATA = true
+		}
+	}
+	if !gotIATA {
+		t.Fatalf("expected at least one observation with non-empty observer_iata")
+	}
+}
+
+func keysOfMap(m map[string]interface{}) []string {
+	out := make([]string, 0, len(m))
+	for k := range m {
+		out = append(out, k)
+	}
+	return out
+}