docs: document installer + portable downloads in en/es

Repo READMEs now show both download flavors side-by-side with
first-launch warnings (SmartScreen, Gatekeeper) and link to the
deeper walkthrough.

USER-GUIDE §1 rewritten from a 9-line stub into six subsections:
- §1.1 Windows: installer (5 steps) + portable (4 steps)
- §1.2 macOS:   DMG (5 steps incl. right-click-Open) + portable
- §1.3 Linux:   AppImage flow (unchanged)
- §1.4 First-launch: port selection, localhost binding, browser open
- §1.5 How the GUI works
- §1.6 System requirements

§6 Troubleshooting picks up portable-specific items: Safari unzip
quirks, antivirus quarantine on Win portable, license file location.

docs/README and Spanish mirrors updated to match.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

docs/README.md

@@ -6,11 +6,13 @@
 
 ## Quick Start
 
-1. Download the installer for your OS from your purchase email.
-2. Run it (no Python knowledge required).
-3. Launch via the desktop shortcut → your default browser opens to a local page.
+1. Download from your purchase email. Two flavors per OS — pick one:
+   - **Installer** (`.dmg` on macOS, `.exe` on Windows) — wires up Desktop + Start Menu / Launchpad shortcuts.
+   - **Portable .zip** — unzip and double-click. No install, no admin rights, runs from anywhere.
+2. Open it (no Python needed; everything is bundled inside).
+3. The app starts a local server and opens your browser. Nothing leaves your machine.
 
-Full instructions: [USER-GUIDE.md](USER-GUIDE.md).
+Full step-by-step including SmartScreen / Gatekeeper workarounds: [USER-GUIDE.md §1](USER-GUIDE.md#1-install).
 
 ## Docs