feat: peek-to-reveal on click/ctrl, pre-commit hooks, devShell, fmt fixes

- Click indicator ring to toggle password peek (persistent click-to-toggle)
- Ctrl-hold transient peek refactored to share peek path
- Cursor always visible (previously hidden at position 0, now shows at top of ring)
- .pre-commit-config.yaml: standard hooks + cargo fmt/clippy
- flake.nix: devShell with cargo, rustc, rustfmt, clippy, cargo-audit, prek
- cargo fmt pass across all source files (trailing whitespace, line wrapping)
- MPRIS error logging (silent failures now logged)
- Dependabot versioning-strategy: "increase" → "auto"

flake.nix

@@ -28,9 +28,28 @@
       nativeBuildInputs = [
         pkgs.pkg-config
         pkgs.rustPlatform.bindgenHook
-        pkgs.rustfmt
-        pkgs.clippy
+      ];
+    };
+
+    devShells.${system}.default = pkgs.mkShell {
+      packages = with pkgs; [
+        cargo
+        rustc
+        rustfmt
+        clippy
+        cargo-audit
+        cargo-deny
+        prek
+        pkg-config
+        rustPlatform.bindgenHook
+        cairo
+        pam
+        gdk-pixbuf
+        librsvg
+        pango
+        libxkbcommon
+        dbus
       ];
     };
   };
-}
+}