feat: add multi-platform packaging and auto-update infrastructure

- Add PyInstaller configuration (clide.spec) for cross-platform builds
- Add build scripts for macOS (DMG), Linux (AppImage), and Windows (Inno Setup)
- Add Gitea Actions CI/CD workflow for automated releases
- Add auto-update service with Gitea API integration
- Add 'clide update' CLI command for checking and installing updates

Packaging outputs:
- macOS: Signed/notarized .app bundle in DMG
- Linux: Portable AppImage (glibc 2.17+)
- Windows: Inno Setup installer

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

packaging/clide.desktop

@@ -0,0 +1,11 @@
+[Desktop Entry]
+Name=Clide
+Comment=TUI IDE for Claude Code
+GenericName=IDE
+Exec=clide
+Icon=clide
+Type=Application
+Categories=Development;IDE;TextEditor;
+Keywords=claude;code;ai;ide;terminal;
+Terminal=true
+StartupNotify=false

packaging/entitlements.plist

@@ -0,0 +1,11 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
+<plist version="1.0">
+<dict>
+    <!-- Required for PyInstaller apps to run with hardened runtime -->
+    <key>com.apple.security.cs.allow-unsigned-executable-memory</key>
+    <true/>
+    <key>com.apple.security.cs.disable-library-validation</key>
+    <true/>
+</dict>
+</plist>