Add filter functionality to CloudWatch Logs tail view

[yimsk]

Feature Request

Add real-time filter functionality to CloudWatch Logs tail view.

Implementation: Client-Side Only ✅

Decision: Simplified to client-side substring match only (removed initial hybrid AWS+Client approach)

Why Client-Only?

• Tail views logs already fetched → client mode sufficient
• AWS filtering only useful for high-volume streams (rare case)
• Hybrid approach added unnecessary complexity
• Avoids confusion about which filter is active

Features Implemented

• Filter activation: / key (consistent with ResourceBrowser)
• Real-time filtering: Filters as user types (instant feedback)
• Filter syntax: Simple case-insensitive substring match
• Clear filter: c key (or clears buffer if no filter active)
• Visual indicators:
  • 🔍 filter: ERROR
  • Filtered count: (45/1,234 lines)
• Status help: Esc:cancel Enter:done when filtering

UI/UX

• / → Activate filter input
• Type → Real-time filtering
• Enter → Done (filter already applied)
• Esc → Cancel/deactivate
• c → Clear filter (or buffer)
• Backspace → Delete chars (fixed via HasActiveInput)

Implementation

• File: internal/view/log_view.go only
• Net change: -68 lines (simpler than initial hybrid)
• No breaking changes: Pure additive feature

Branch

feature/120-log-tail-filter

Status

✅ Implemented
✅ Tests pass
✅ Backspace handling fixed
✅ Simplified from hybrid to client-only
⏳ Ready for manual testing + PR