Complete ORM gaps + server features + module depth push

ORM:
- SQL Constraints support (Model.AddSQLConstraint, applied in InitDatabase)
- Translatable field Read (ir_translation lookup for non-en_US)
- active_test filter in SearchCount + ReadGroup (consistency with Search)
- Environment.Ref() improved (format validation, parameterized query)

Server:
- /web/action/run endpoint (server action execution stub)
- /web/model/get_definitions (field metadata for multiple models)
- Binary field serving rewritten: reads from DB, falls back to SVG
  with record initial (fixes avatar/logo rendering)

Business modules deepened:
- Account: action_post validation (partner, lines), sequence numbering
  (JOURNAL/YYYY/NNNN), action_register_payment, remove_move_reconcile
- Sale: action_cancel, action_draft, action_view_invoice
- Purchase: button_draft
- Stock: action_cancel on picking
- CRM: action_set_won_rainbowman, convert_opportunity
- HR: hr.contract model (employee, wage, dates, state)
- Project: action_blocked, task stage seed data

Views:
- Cancel/Reset buttons in sale.form header
- Register Payment button in invoice.form (visible when posted+unpaid)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

pkg/server/views.go

@@ -1,12 +1,38 @@
 package server
 
 import (
+	"encoding/json"
 	"fmt"
+	"net/http"
 	"strings"
 
 	"odoo-go/pkg/orm"
 )
 
+// handleGetDefinitions returns field definitions for one or more models.
+// Mirrors: odoo/addons/web/controllers/model.py Model.get_definitions()
+func (s *Server) handleGetDefinitions(w http.ResponseWriter, r *http.Request) {
+	if r.Method != http.MethodPost {
+		http.Error(w, "Method not allowed", http.StatusMethodNotAllowed)
+		return
+	}
+	var req JSONRPCRequest
+	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
+		s.writeJSONRPC(w, nil, nil, &RPCError{Code: -32700, Message: "Parse error"})
+		return
+	}
+	var params struct {
+		Models []string `json:"model_names"`
+	}
+	json.Unmarshal(req.Params, &params)
+
+	result := make(map[string]interface{})
+	for _, modelName := range params.Models {
+		result[modelName] = fieldsGetForModel(modelName)
+	}
+	s.writeJSONRPC(w, req.ID, result, nil)
+}
+
 // handleGetViews implements the get_views method.
 // Mirrors: odoo/addons/base/models/ir_ui_view.py get_views()
 func handleGetViews(env *orm.Environment, model string, params CallKWParams) (interface{}, *RPCError) {