feat: complete Rust-to-Go rewrite with Bubbletea v2

Rewrites oxker from Rust/ratatui to Go/Bubbletea, migrated to the
Bubbletea v2 API (charm.land/bubbletea/v2). Removes all original Rust
source files and legacy Go modules (internal/ui, internal/input, bubbles).

Key changes:
- View() returns tea.View with declarative AltScreen and MouseMode
- KeyMsg → KeyPressMsg, MouseMsg → MouseClickMsg/WheelMsg/MotionMsg/ReleaseMsg
- execWriteKey rewritten for v2 key fields (Code/Mod/Text)
- Mouse toggle via View field instead of imperative commands
- Filter/search text input uses msg.Text for v2 space key compat

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

cmd/oxker/main.go

@@ -0,0 +1,40 @@
+package main
+
+import (
+	"fmt"
+	"os"
+
+	tea "charm.land/bubbletea/v2"
+	"github.com/oxker/oxker/internal/app"
+)
+
+func main() {
+	// Parse command-line arguments
+	cliArgs, err := ParseCLIArgs()
+	if err != nil {
+		fmt.Fprintf(os.Stderr, "Error parsing CLI args: %v\n", err)
+		os.Exit(1)
+	}
+
+	// Load configuration
+	cfg, err := LoadConfig(cliArgs)
+	if err != nil {
+		fmt.Fprintf(os.Stderr, "Error loading config: %v\n", err)
+		os.Exit(1)
+	}
+
+	// Debug mode - no TUI
+	if !cfg.GUI {
+		ShowDebugInfo(nil)
+		return
+	}
+
+	// Create and start the Bubble Tea program
+	// AltScreen and MouseMode are now controlled via View() return value
+	p := tea.NewProgram(app.New(cfg))
+
+	if _, err := p.Run(); err != nil {
+		fmt.Fprintf(os.Stderr, "Error: %v\n", err)
+		os.Exit(1)
+	}
+}