Add plant catalog backend: CRUD + seeded built-ins (#12)

Extends the plants store (which had only the /full read side) with full
catalog CRUD, adds a service layer with visibility/immutability rules, REST
endpoints, and a seed migration of ~32 built-ins.

- 0003_seed_plants.sql: 32 built-in plants (owner_id NULL, read-only), seeded
  once by the version-tracked migration runner.
- store: ListPlantsForActor (built-ins + own), Get/Create/Update/Delete +
  CountPlantingsForPlant; isForeignKeyViolation backstop for the RESTRICT FK.
- service: built-ins are read-only (ErrForbidden); another user's plants are
  invisible (ErrNotFound); delete of a referenced plant → ErrPlantInUse (409);
  validation mirrors the schema (category enum, spacing>0, hex color, icon).
- api: GET,POST /plants and PATCH,DELETE /plants/:id with the version guard.
- Made the migration-count store tests derive their expectation from the files
  so future migrations don't break them.

Service + API tests cover visibility, built-in immutability, validation,
version conflict, and delete-in-use.

Co-Authored-By: Claude Opus 4.8 (1M context) <[email protected]>
Claude-Session: https://claude.ai/code/session_01JdQpdYYsTgtkJBxbcpAszi

internal/api/plants.go

@@ -0,0 +1,133 @@
+package api
+
+import (
+	"encoding/json"
+	"errors"
+	"net/http"
+
+	"github.com/gin-gonic/gin"
+
+	"gitea.stevedudenhoeffer.com/steve/pansy/internal/domain"
+	"gitea.stevedudenhoeffer.com/steve/pansy/internal/service"
+)
+
+// plantCreateRequest is the body for POST /plants. spacingCm is centimeters;
+// color is a hex string; icon is an emoji. daysToMaturity is optional.
+type plantCreateRequest struct {
+	Name           string  `json:"name" binding:"required"`
+	Category       string  `json:"category" binding:"required"`
+	SpacingCM      float64 `json:"spacingCm"`
+	Color          string  `json:"color" binding:"required"`
+	Icon           string  `json:"icon" binding:"required"`
+	DaysToMaturity *int    `json:"daysToMaturity"`
+	Notes          string  `json:"notes"`
+}
+
+func (r plantCreateRequest) toInput() service.PlantInput {
+	return service.PlantInput{
+		Name: r.Name, Category: r.Category, SpacingCM: r.SpacingCM,
+		Color: r.Color, Icon: r.Icon, DaysToMaturity: r.DaysToMaturity, Notes: r.Notes,
+	}
+}
+
+// plantUpdateRequest is the body for PATCH /plants/:id: every field optional
+// (absent = unchanged), plus the required current version. daysToMaturity is
+// json.RawMessage so an explicit null (clear it) is distinct from an absent
+// field (unchanged).
+type plantUpdateRequest struct {
+	Name           *string         `json:"name"`
+	Category       *string         `json:"category"`
+	SpacingCM      *float64        `json:"spacingCm"`
+	Color          *string         `json:"color"`
+	Icon           *string         `json:"icon"`
+	DaysToMaturity json.RawMessage `json:"daysToMaturity"`
+	Notes          *string         `json:"notes"`
+	Version        int64           `json:"version" binding:"required,min=1"`
+}
+
+func (r plantUpdateRequest) toPatch() (service.PlantPatch, error) {
+	days, setDays, err := parseNullableInt(r.DaysToMaturity)
+	if err != nil {
+		return service.PlantPatch{}, err
+	}
+	return service.PlantPatch{
+		Name: r.Name, Category: r.Category, SpacingCM: r.SpacingCM,
+		Color: r.Color, Icon: r.Icon,
+		SetDays: setDays, DaysToMaturity: days, Notes: r.Notes,
+	}, nil
+}
+
+// parseNullableInt decodes a JSON number|null field into (value, present).
+// Absent → (nil, false); null → (nil, true); 42 → (&42, true). A non-integer
+// value is an error.
+func parseNullableInt(raw json.RawMessage) (value *int, present bool, err error) {
+	if len(raw) == 0 {
+		return nil, false, nil
+	}
+	if err := json.Unmarshal(raw, &value); err != nil {
+		return nil, false, err
+	}
+	return value, true, nil
+}
+
+func (h *handlers) listPlants(c *gin.Context) {
+	plants, err := h.svc.ListPlants(c.Request.Context(), mustActor(c).ID)
+	if err != nil {
+		writeServiceError(c, err)
+		return
+	}
+	c.JSON(http.StatusOK, plants)
+}
+
+func (h *handlers) createPlant(c *gin.Context) {
+	var req plantCreateRequest
+	if err := c.ShouldBindJSON(&req); err != nil {
+		writeAPIError(c, http.StatusBadRequest, "INVALID_INPUT", "name, category, color and icon are required")
+		return
+	}
+	p, err := h.svc.CreatePlant(c.Request.Context(), mustActor(c).ID, req.toInput())
+	if err != nil {
+		writeServiceError(c, err)
+		return
+	}
+	c.JSON(http.StatusCreated, p)
+}
+
+func (h *handlers) updatePlant(c *gin.Context) {
+	id, ok := parseIDParam(c, "id")
+	if !ok {
+		return
+	}
+	var req plantUpdateRequest
+	if err := c.ShouldBindJSON(&req); err != nil {
+		writeAPIError(c, http.StatusBadRequest, "INVALID_INPUT", "a current version is required")
+		return
+	}
+	patch, err := req.toPatch()
+	if err != nil {
+		writeAPIError(c, http.StatusBadRequest, "INVALID_INPUT", "invalid update payload")
+		return
+	}
+	p, err := h.svc.UpdatePlant(c.Request.Context(), mustActor(c).ID, id, patch, req.Version)
+	if err != nil {
+		if errors.Is(err, domain.ErrVersionConflict) {
+			writeVersionConflict(c, p)
+			return
+		}
+		writeServiceError(c, err)
+		return
+	}
+	c.JSON(http.StatusOK, p)
+}
+
+func (h *handlers) deletePlant(c *gin.Context) {
+	id, ok := parseIDParam(c, "id")
+	if !ok {
+		return
+	}
+	if err := h.svc.DeletePlant(c.Request.Context(), mustActor(c).ID, id); err != nil {
+		writeServiceError(c, err)
+		return
+	}
+	c.Status(http.StatusNoContent)
+}