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/service/db.go

@@ -7,6 +7,7 @@ import (
 	"crypto/rand"
 	"fmt"
 	"log"
+	"strings"
 
 	"github.com/jackc/pgx/v5"
 	"github.com/jackc/pgx/v5/pgxpool"
@@ -115,6 +116,34 @@ func InitDatabase(ctx context.Context, pool *pgxpool.Pool) error {
 		}
 	}
 
+	// Phase 4c: SQL constraints
+	// Mirrors: _sql_constraints in Odoo models
+	for name, m := range models {
+		if m.IsAbstract() {
+			continue
+		}
+		for _, sc := range m.SQLConstraints {
+			constraintName := strings.ReplaceAll(name, ".", "_") + "_" + sc.Name
+			query := fmt.Sprintf(
+				`DO $$ BEGIN
+					ALTER TABLE %q ADD CONSTRAINT %s %s;
+				EXCEPTION WHEN duplicate_object THEN NULL;
+				END $$`,
+				m.Table(), constraintName, sc.Definition,
+			)
+			sp, spErr := tx.Begin(ctx)
+			if spErr != nil {
+				continue
+			}
+			if _, err := sp.Exec(ctx, query); err != nil {
+				log.Printf("db: constraint %s: %v", constraintName, err)
+				sp.Rollback(ctx)
+			} else {
+				sp.Commit(ctx)
+			}
+		}
+	}
+
 	// Phase 5: Seed ir_model and ir_model_fields with model metadata.
 	// This is critical because ir.rule joins through ir_model to find rules for a model.
 	// Mirrors: odoo/modules/loading.py load_module_graph() → _setup_base()