feat(contacts): add contacts page with per-store management and supplier email field

- New contacts table (group_id, name, role, phone, email, notes) per store
- Suppliers table: add email field with form and card display
- Page /contacts: two-column layout (suppliers read-only / free contacts CRUD)
- Permissions: read all roles, create/edit/delete admin + directeur + manager
- Admin can filter contacts by store; other roles see their own stores only
- Migration SQL: 20260515_add_contacts_and_supplier_email.sql

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

migrations/20260515_add_contacts_and_supplier_email.sql

@@ -0,0 +1,21 @@
+-- Migration: Ajout email fournisseurs + table contacts par magasin
+-- Created: 2026-05-15
+
+-- Ajout du champ email sur les fournisseurs
+ALTER TABLE suppliers ADD COLUMN IF NOT EXISTS email VARCHAR(255);
+
+-- Table des contacts libres, rattachés à un magasin
+CREATE TABLE IF NOT EXISTS contacts (
+  id SERIAL PRIMARY KEY,
+  group_id INTEGER NOT NULL REFERENCES groups(id) ON DELETE CASCADE,
+  name VARCHAR(255) NOT NULL,
+  role VARCHAR(255),
+  phone VARCHAR(50),
+  email VARCHAR(255),
+  notes TEXT,
+  created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP,
+  updated_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP
+);
+
+-- Index pour recherche rapide par magasin
+CREATE INDEX IF NOT EXISTS idx_contacts_group_id ON contacts(group_id);