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>

internal/utils/ratelimiter.go

@@ -0,0 +1,29 @@
+package utils
+
+import (
+	"time"
+)
+
+type RateLimiter struct {
+	lastTime    time.Time
+	minInterval time.Duration
+}
+
+func NewRateLimiter(interval time.Duration) *RateLimiter {
+	return &RateLimiter{
+		minInterval: interval,
+	}
+}
+
+func (r *RateLimiter) Allow() bool {
+	now := time.Now()
+	if now.Sub(r.lastTime) >= r.minInterval {
+		r.lastTime = now
+		return true
+	}
+	return false
+}
+
+func (r *RateLimiter) Reset() {
+	r.lastTime = time.Time{}
+}