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.

scripts/bump_version.sh

@@ -0,0 +1,108 @@
+#!/usr/bin/env bash
+# -----------------------------------------------------------------------------
+# ObsiGate — version bump helper (SemVer MAJOR.MINOR.PATCH)
+#
+# The canonical version is the latest release tag. This tool inspects the
+# commits since that tag and decides the next version from their type
+# (Conventional Commits), then creates and pushes the new tag:
+#
+#   breaking change / `!:` / "BREAKING CHANGE"  ->  MAJOR bump  (x.0.0)
+#   feat / feature                              ->  MINOR bump  (x.y.0)
+#   anything else (fix, perf, refactor, ...)    ->  PATCH bump  (x.y.z)
+#
+# Usage:
+#   scripts/bump_version.sh [--major|--minor|--patch] [--dry-run] [--push]
+#
+#   --dry-run : only print the computed next version, do not tag.
+#   --push    : also `git push origin` the new tag (default: local only).
+#   --major|--minor|--patch : force the increment, overriding commit detection.
+#
+# Examples:
+#   scripts/bump_version.sh --dry-run            # preview next version
+#   scripts/bump_version.sh                       # tag locally per commits
+#   scripts/bump_version.sh --patch --push        # force patch + push
+# -----------------------------------------------------------------------------
+set -euo pipefail
+
+cd "$(git rev-parse --show-toplevel)"   # run from repo root regardless of cwd
+BRANCH="$(git branch --show-current)"
+
+# ── Parse args ────────────────────────────────────────────────────────────
+FORCE=""; DRY_RUN=0; DO_PUSH=0
+for a in "$@"; do
+  case "$a" in
+    --major) FORCE=major ;;
+    --minor) FORCE=minor ;;
+    --patch) FORCE=patch ;;
+    --dry-run) DRY_RUN=1 ;;
+    --push) DO_PUSH=1 ;;
+    *) echo "✗ Argument inconnu: $a"; exit 2 ;;
+  esac
+done
+
+# ── Current version = latest tag base ─────────────────────────────────────
+CURRENT="$(git describe --tags --abbrev=0 2>/dev/null || echo "0.0.0")"
+CURRENT="${CURRENT#v}"
+IFS='.' read -r MAJ MIN PAT <<< "$CURRENT"
+MAJ="${MAJ:-0}"; MIN="${MIN:-0}"; PAT="${PAT:-0}"
+
+echo "Version actuelle : $CURRENT  (branche: $BRANCH)"
+
+# ── Detect bump type from commits since last tag ──────────────────────────
+if [ -z "$FORCE" ]; then
+  # Use HEAD~1..HEAD when no tag exists yet (all commits "since" nothing).
+  RANGE="${CURRENT#0.0.0}" # if 0.0.0 fallback there may be no tag at all
+  if git rev-parse "v${CURRENT}" >/dev/null 2>&1; then
+    RANGE="v${CURRENT}..HEAD"
+  else
+    RANGE="HEAD~10..HEAD"
+    echo "⚠ Aucun tag v${CURRENT} trouvé — analyse des 10 derniers commits."
+  fi
+  LOG="$(git log --format='%s%n%b' "$RANGE" 2>/dev/null || true)"
+
+  BUMP="patch"   # default
+  if echo "$LOG" | grep -qE '^[a-zA-Z]+\([^)]*\)!:|\!:\s|BREAKING CHANGE:'; then
+    BUMP="major"
+  elif echo "$LOG" | grep -qiE '^(feat|feature)(\(|:|\s)'; then
+    BUMP="minor"
+  fi
+  # If nothing meaningful in range, keep patch
+  echo "Détection (${RANGE}) : changement ${BUMP}"
+else
+  BUMP="$FORCE"
+  echo "Incrément forcé  : ${BUMP}"
+fi
+
+# ── Compute next version ──────────────────────────────────────────────────
+case "$BUMP" in
+  major) MAJ=$((MAJ + 1)); MIN=0; PAT=0 ;;
+  minor) MIN=$((MIN + 1)); PAT=0 ;;
+  *)     PAT=$((PAT + 1)) ;;
+esac
+NEXT="${MAJ}.${MIN}.${PAT}"
+
+# ── Guard: tag already exists? ────────────────────────────────────────────
+if git rev-parse "v${NEXT}" >/dev/null 2>&1; then
+  echo "✗ Le tag v${NEXT} existe déjà. Corrigez l'incrément ou retirez le tag."
+  exit 1
+fi
+
+if [ "$DRY_RUN" = "1" ]; then
+  echo "── DRY RUN ─────────────────────────────"
+  echo "   Prochain tag : v${NEXT}"
+  echo "   (aucun tag créé)"
+  exit 0
+fi
+
+# ── Create tag ────────────────────────────────────────────────────────────
+git tag -a "v${NEXT}" -m "Release v${NEXT} (${BUMP} bump depuis v${CURRENT})"
+echo "✓ Tag créé localement : v${NEXT}"
+
+if [ "$DO_PUSH" = "1" ]; then
+  git push origin "v${NEXT}"
+  echo "✓ Tag poussé : v${NEXT}"
+else
+  echo "ℹ Tag local uniquement. Poussez avec: git push origin v${NEXT}"
+fi
+
+echo "Done."