Ajout de l'application Presencia (gestion des présences multi-sociétés)

Application complète : API Node/Express + PostgreSQL, frontend HTML/JS
mono-page, et déploiement Docker sur ports non standards (8781/4790/6543).

- Cadres : calendrier mensuel, saisie de présence par demi-journée
  (présent/absent/congé/RTT), validation de fin de mois qui verrouille
  leurs propres saisies.
- Admin : gestion des sociétés et utilisateurs (rattachement société <->
  cadre), consultation de tous les plannings, validation d'une société
  entière une fois tous ses cadres validés, réouverture en cas de
  correction, export PDF et Excel par société/mois.

backend/migrations/001_init.sql

@@ -0,0 +1,59 @@
+-- Presencia schema
+
+CREATE TYPE user_role AS ENUM ('admin', 'cadre');
+CREATE TYPE half_day_period AS ENUM ('AM', 'PM');
+CREATE TYPE attendance_status AS ENUM ('present', 'absent', 'conge', 'rtt');
+
+CREATE TABLE companies (
+  id SERIAL PRIMARY KEY,
+  name VARCHAR(255) NOT NULL UNIQUE,
+  created_at TIMESTAMPTZ NOT NULL DEFAULT now()
+);
+
+CREATE TABLE users (
+  id SERIAL PRIMARY KEY,
+  full_name VARCHAR(255) NOT NULL,
+  email VARCHAR(255) NOT NULL UNIQUE,
+  password_hash VARCHAR(255) NOT NULL,
+  role user_role NOT NULL DEFAULT 'cadre',
+  company_id INTEGER REFERENCES companies(id) ON DELETE SET NULL,
+  active BOOLEAN NOT NULL DEFAULT true,
+  created_at TIMESTAMPTZ NOT NULL DEFAULT now()
+);
+
+CREATE INDEX idx_users_company ON users(company_id);
+
+CREATE TABLE attendance_entries (
+  id SERIAL PRIMARY KEY,
+  user_id INTEGER NOT NULL REFERENCES users(id) ON DELETE CASCADE,
+  entry_date DATE NOT NULL,
+  period half_day_period NOT NULL,
+  status attendance_status NOT NULL,
+  updated_at TIMESTAMPTZ NOT NULL DEFAULT now(),
+  UNIQUE(user_id, entry_date, period)
+);
+
+CREATE INDEX idx_attendance_user_date ON attendance_entries(user_id, entry_date);
+
+-- Cadre self-validation of a given month (locks that month's entries for the cadre)
+CREATE TABLE month_locks (
+  id SERIAL PRIMARY KEY,
+  user_id INTEGER NOT NULL REFERENCES users(id) ON DELETE CASCADE,
+  year INTEGER NOT NULL,
+  month INTEGER NOT NULL CHECK (month BETWEEN 1 AND 12),
+  cadre_validated BOOLEAN NOT NULL DEFAULT false,
+  cadre_validated_at TIMESTAMPTZ,
+  UNIQUE(user_id, year, month)
+);
+
+-- Admin validation of a whole company for a given month (requires all cadres validated first)
+CREATE TABLE company_month_validations (
+  id SERIAL PRIMARY KEY,
+  company_id INTEGER NOT NULL REFERENCES companies(id) ON DELETE CASCADE,
+  year INTEGER NOT NULL,
+  month INTEGER NOT NULL CHECK (month BETWEEN 1 AND 12),
+  admin_validated BOOLEAN NOT NULL DEFAULT false,
+  admin_validated_at TIMESTAMPTZ,
+  admin_validated_by INTEGER REFERENCES users(id),
+  UNIQUE(company_id, year, month)
+);