Address seed-packet review: 413 mapping, deadline, rollback, dedup

Gadfly findings on #94, the real ones:

- scanSeedPacket extends only the READ deadline; a slow upload + a live
  vision call runs past the server's absolute 30s WriteTimeout and the
  successful response is silently dropped (the #78 failure mode). Extend
  the write deadline too (scanWriteTimeout).
- An oversized upload tripping MaxBytesReader was mapped to 400; it's 413.
  Detect *http.MaxBytesError and report IMAGE_TOO_LARGE.
- Split imagenorm error mapping: ErrTooLarge->413, ErrUnsupported->400,
  genuine read/encode faults (and a failed file.Open)->500, not 400.
- CreateFromPacket discarded the plant it created when the lot then
  failed, contradicting its own doc. Roll the new plant back instead so
  the confirm is all-or-nothing (a fresh plant has no lots/plantings, so
  the delete is safe; log-and-continue on cleanup failure).
- Dedup: packetLotRequest and seedLotCreateRequest shared every lot
  field. Extract a seedLotFields base both use. validCategory now reuses
  plantCategories. EffectiveConfig resolves agent+vision from one
  settings-row read instead of two.
- capabilities swallowed an EffectiveVision error silently; log it.
- vision test hand-copied Extract's body (drift risk). Split generate()
  out of Extract so the hermetic test drives the real request builder.

Tests: rollback-on-lot-failure (service), oversized->413 (api).

Co-Authored-By: Claude Opus 4.8 (1M context) <[email protected]>
Claude-Session: https://claude.ai/code/session_01H3zbym8Doka2d7D48maSgZ

internal/service/seed_packet_test.go

@@ -180,6 +180,41 @@ func TestCreateFromPacketExistingPlant(t *testing.T) {
 	}
 }
 
+// TestCreateFromPacketRollsBackNewPlantOnLotFailure: if the lot fails after a new
+// plant was created for the confirm, the plant is rolled back so a bad lot can't
+// strand a half-made catalog entry the user never asked for on its own.
+func TestCreateFromPacketRollsBackNewPlantOnLotFailure(t *testing.T) {
+	ctx := context.Background()
+	s, owner := visionTestService(t, vision.SeedPacket{}, nil)
+
+	before, err := s.ListPlants(ctx, owner)
+	if err != nil {
+		t.Fatalf("list before: %v", err)
+	}
+
+	// A bogus unit makes CreateSeedLot fail AFTER the plant is created.
+	_, err = s.CreateFromPacket(ctx, owner, PacketConfirm{
+		NewPlant: &PlantInput{Name: "Rollback Garlic", Category: domain.CategoryVegetable, SpacingCM: 15, Color: "#4a7c3f", Icon: "🧄"},
+		Lot:      SeedLotInput{Vendor: "Johnny's", Quantity: 8, Unit: "furlongs"},
+	})
+	if !errors.Is(err, domain.ErrInvalidInput) {
+		t.Fatalf("err = %v, want ErrInvalidInput from the bad unit", err)
+	}
+
+	after, err := s.ListPlants(ctx, owner)
+	if err != nil {
+		t.Fatalf("list after: %v", err)
+	}
+	if len(after) != len(before) {
+		t.Errorf("plant count %d → %d: the rolled-back plant was left behind", len(before), len(after))
+	}
+	for _, p := range after {
+		if p.Name == "Rollback Garlic" {
+			t.Errorf("plant %q survived a failed lot; rollback didn't fire", p.Name)
+		}
+	}
+}
+
 // TestCreateFromPacketExactlyOne: both or neither of PlantID/NewPlant is refused,
 // so an ambiguous confirm can't silently pick.
 func TestCreateFromPacketExactlyOne(t *testing.T) {