docs: add INSTALL.md and update project documentation for release pipeline

Co-authored-by: Junie <junie@jetbrains.com>

docs/plans/feature-6-release-pipeline.md

@@ -0,0 +1,23 @@
+# Feature 6: Build Automation & Release Pipeline
+
+**Status:** ✅ **Completed**
+
+## Context
+Automated multi-platform packaging and release pipeline for WoW Backup using GitHub Actions. Whenever changes are merged/pushed to the `main` branch, the pipeline calculates the next release version and tag, compiles native distributables for macOS, Windows, and Linux, and attaches all packaged binaries to a published GitHub Release.
+
+## Deliverables
+1. **Dynamic Versioning in Gradle**:
+   - `composeApp/build.gradle.kts` dynamically reads `appVersion` via `-PappVersion=...` or defaults to `1.0.0`.
+   - `BuildConfig.kt` and native distribution packaging tasks respect the injected version.
+2. **GitHub Actions Workflow (`.github/workflows/release.yml`)**:
+   - Automated semantic patch version computation and git tagging on push to `main` and `workflow_dispatch`.
+   - Parallel runner matrix (`macos-latest`, `windows-latest`, `ubuntu-latest`) packaging `.dmg`, `.msi`, and `.deb`.
+   - Automated GitHub Release creation with attached artifacts and release notes.
+3. **Installation Guide (`INSTALL.md`)**:
+   - Detailed user installation guide for macOS (Gatekeeper bypass), Windows (SmartScreen bypass), and Linux (APT/DPKG).
+   - Linked directly from `README.md`.
+
+## Verification
+- `./gradlew :composeApp:generateBuildConfig -PappVersion=1.2.3` generates `BuildConfig.VERSION = "1.2.3"`.
+- Packaging tasks (`packageDmg`, `packageMsi`, `packageDeb`) are wired and functional.
+- Workflow YAML syntax validated.