Add Go project scaffold for Wails v2 SSH/Telnet/RAW TCP client

- go.mod with Wails v2.9.2, x/crypto, go-sqlite3, go-keyring, uuid
- cmd/app/main.go: Wails entry point (Nexus Terminal, 1400x900, #1a1a2e)
- internal/app/app.go: lifecycle (Startup/Shutdown/DomReady)
- internal/models/models.go: full model definitions (Profile, SSHConfig,
  TelnetConfig, RAWConfig, SessionInfo, KnownHost, AppPreferences, etc.)
- internal/models/defaults.go: default values and NewProfile factory
- internal/validation/validation.go: thorough field-level validation
- frontend/embed.go: embedded frontend assets
- Updated existing storage, secrets, config to match new model structure

.gitignore

@@ -0,0 +1,38 @@
+# Build output
+build/
+dist/
+
+# Dependencies
+vendor/
+frontend/node_modules/
+frontend/src/js/lib/
+frontend/src/css/lib/
+
+# IDE
+.idea/
+.vscode/
+*.swp
+*.swo
+*~
+
+# OS
+.DS_Store
+Thumbs.db
+
+# Test
+coverage.out
+coverage.html
+
+# Binaries
+*.exe
+*.dll
+*.so
+*.dylib
+
+# Debug
+__debug_bin*
+
+# Application data (never commit)
+*.db
+*.sqlite
+vault.json