feat: versioning SemVer MAJOR.MINOR.PATCH basé sur git describe

- backend/version.py: get_version() lit git describe --tags (ex: 1.8.0-301-gabc1234)
- main.py: FastAPI version = get_version() dynamique
- build.rs: injecte GIT_VERSION, GIT_HASH, SEMVER depuis git describe
- main.rs: ABOUT_MSG, get_version(), log utilisent GIT_VERSION
- Format: MAJOR.MINOR.PATCH[-commits-gHASH] (ex: 1.8.0, 1.8.0-3-gabc1234)
- Fallback: VERSION file ou 0.0.0-dev si Git indisponible

desktop/src/main.rs

@@ -240,9 +240,7 @@ fn get_backend_url() -> String {
 
 #[tauri::command]
 fn get_version() -> String {
-    let cargo_version = env!("CARGO_PKG_VERSION");
-    let git_hash = env!("GIT_HASH");
-    format!("v{}-{}", cargo_version, git_hash)
+    env!("GIT_VERSION").to_string()
 }
 
 #[tauri::command]
@@ -422,7 +420,7 @@ fn get_window_state() -> AppConfig {
 
 // Build About message once at compile time
 const ABOUT_MSG: &str = concat!(
-    "ObsiGate Desktop v", env!("CARGO_PKG_VERSION"), "-", env!("GIT_HASH"),
+    "ObsiGate Desktop ", env!("GIT_VERSION"),
     "\\n\\nPorte d\\'entrée native pour vos vaults Obsidian.",
     "\\nConstruit avec Tauri + Rust.",
     "\\n\\n© Bruno Charest — Licence MIT",
@@ -447,8 +445,7 @@ fn main() {
         })
         .try_init();
 
-    let version_str = format!("v{}-{}", env!("CARGO_PKG_VERSION"), env!("GIT_HASH"));
-    info!("ObsiGate Desktop {} starting", version_str);
+    info!("ObsiGate Desktop {} starting", env!("GIT_VERSION"));
 
     // Resolve exe directory
     let exe_dir = std::env::current_exe()