Add Makefile, package.json, and initial configuration for VitePress and Slidev integration

- Introduced a Makefile for streamlined commands related to building, running, and managing presentations.
- Created package.json to define project metadata, dependencies, and scripts for development and testing.
- Added .gitignore entries to exclude build artifacts and temporary files from version control.
- Included playwright.config.mjs for end-to-end testing setup with Playwright.
- Added README.md for project documentation, outlining setup instructions and development guidelines.

tests/site-base.test.mjs

@@ -0,0 +1,46 @@
+import { test, describe, beforeEach } from 'node:test'
+import assert from 'node:assert'
+import { getSiteBase, sitePath, vitepressAppBase } from '../tools/site-base.mjs'
+
+describe('site-base (SITE_BASE / chemins statiques)', () => {
+  beforeEach(() => {
+    delete process.env.SITE_BASE
+    delete process.env.TALKS_PORTAL_DEV
+  })
+
+  test('défaut : même comportement que la racine du site', () => {
+    assert.strictEqual(getSiteBase(), '')
+    assert.strictEqual(sitePath('/slides/foo/'), '/slides/foo/')
+    assert.strictEqual(sitePath('/presentations/bar/'), '/presentations/bar/')
+  })
+
+  test('sous-chemin sans slash final', () => {
+    process.env.SITE_BASE = '/mon-depot'
+    assert.strictEqual(getSiteBase(), '/mon-depot')
+    assert.strictEqual(sitePath('/slides/foo/'), '/mon-depot/slides/foo/')
+  })
+
+  test('sous-chemin avec slash final', () => {
+    process.env.SITE_BASE = '/repo/'
+    assert.strictEqual(getSiteBase(), '/repo')
+    assert.strictEqual(sitePath('/slides/x/'), '/repo/slides/x/')
+  })
+
+  test('chemins relatifs normalisés', () => {
+    delete process.env.SITE_BASE
+    assert.strictEqual(sitePath('slides/x/'), '/slides/x/')
+  })
+
+  test('SITE_BASE vide explicite : traité comme /', () => {
+    process.env.SITE_BASE = ''
+    assert.strictEqual(getSiteBase(), '')
+  })
+
+  test('TALKS_PORTAL_DEV=1 : ignore SITE_BASE (dev local)', () => {
+    process.env.TALKS_PORTAL_DEV = '1'
+    process.env.SITE_BASE = '/pages-projet/'
+    assert.strictEqual(getSiteBase(), '')
+    assert.strictEqual(sitePath('/slides/a/'), '/slides/a/')
+    assert.strictEqual(vitepressAppBase(), '/')
+  })
+})