feat(version): version x.y.z propre et cohérente partout + bump script

Corrige l'incoherence d'affichage (page principale 0.0.0-dev vs a propos
v2.0.0-dev) et unifie la gestion de version sur une seule source de verite.

Backend:
- version.py: get_version() retourne toujours le tag x.y.z propre du dernier
  tag (plus de 0.0.0-dev / -N-gHASH dans l'UI). Ajout get_git_describe() et
  get_git_commit() pour le detail.
- main.py: /api/health expose git_describe + git_commit (nouveaux champs).

Frontend:
- modale A propos (populateAbout): version + commit lus depuis /api/health,
  suppression du hardcode v2.0.0-dev dans index.html.
- section config A propos (loadAbout): lit health.version, plus de state.
  APP_VERSION obsolete.
- badge header: fetch /api/health (fallback neutre '...').
- state.js: suppression de APP_VERSION (1.5.0) devenu mort; imports nettoyes.

Script:
- scripts/bump_version.sh: incrementation SemVer selon les commits
  (breaking->major, feat->minor, sinon patch), creer/pousser le tag vX.Y.Z.

Tests: 507 passed, frontend validators OK.

frontend/js/app.js

@@ -5,7 +5,6 @@
 import * as UI from './ui.js';
 import * as Utils from './utils.js';
 import { initI18n, t } from './i18n.js';
-import { state } from './state.js';
 import { initAIFab } from './ai-fab.js';
 
 // Wire up AI toolbar toast (avoids circular import in utils.js)
@@ -117,7 +116,7 @@ document.addEventListener("DOMContentLoaded", () => {
   // Show version in header — always visible, fallback before the async fetch
   const versionBadge = document.getElementById('version-badge');
   if (versionBadge) {
-    versionBadge.textContent = window.__OBSIGATE_VERSION || state.APP_VERSION || 'dev';
+    versionBadge.textContent = window.__OBSIGATE_VERSION || '…';
   }
   fetch('/api/health')
     .then(r => r.json())

frontend/js/config.js

@@ -923,8 +923,7 @@ function loadAbout() {
         title: t("about.section_app"),
         rows: [
           [t("about.name"), "ObsiGate"],
-          [t("about.version"), state.APP_VERSION],
-          [t("about.api_version"), health.version || "—"],
+          [t("about.version"), health.version || "—"],
           [t("about.status"), health.status || "—"],
         ],
       },
@@ -1653,7 +1652,7 @@ function initAboutModal() {
   document.addEventListener('keydown', function(e) { if (e.key === 'Escape' && overlay.classList.contains('active')) overlay.classList.remove('active'); });
 
   function populateAbout() {
-    // Live stats from health endpoint
+    // Live stats + version from health endpoint (single source of truth)
     fetch('/api/health')
       .then(function(r) { return r.json(); })
       .then(function(d) {
@@ -1661,6 +1660,11 @@ function initAboutModal() {
         var vEl = document.getElementById('about-stat-vaults');
         if (fEl) fEl.textContent = d.total_files || '—';
         if (vEl) vEl.textContent = d.vaults || '—';
+        // Clean x.y.z version (not hardcoded) + git detail
+        var versionEl = document.getElementById('about-version');
+        if (versionEl && d.version) versionEl.textContent = d.version;
+        var commitEl = document.getElementById('about-commit');
+        if (commitEl) commitEl.textContent = d.git_describe || d.git_commit || '—';
       })
       .catch(function() {});
 

frontend/js/state.js

@@ -2,8 +2,6 @@
    Use state.xxx to read/write any value. ES module imports are read-only,
    so we export a single mutable object instead of individual let bindings. */
 export const state = {
-  APP_VERSION: "1.5.0",
-
   // Core navigation
   currentVault: null,
   currentPath: null,