feat: update external success screen text and image

[jvsena42]

FIGMA

This PR:

1. Updates the external success screen title from "Connection initiated" to "Channel opening"
2. Replaces the switch box image with a lightning bolt illustration
3. Adds a dedicated "Spending Balance" nav title for the success screen
4. Translates all new and updated strings across 15 locales

Description

Updates the external node connection success screen to match the new Figma design. The title now reads "Channel Opening" (with "Opening" accented in purple), the illustration is a lightning bolt, and the nav bar shows "Spending Balance" instead of the shared "Lightning Connection" title.

Preview

QA Notes

1. Open the app and navigate to Transfer → External Node
2. Complete the external connection flow
3. Verify the success screen shows:
   • Nav title: "Spending Balance"
   • Title: "Channel" on line 1, "Opening" on line 2 in purple
   • Lightning bolt illustration (not the old switch box)
   • Description text unchanged
4. Switch device language to each supported locale and verify the title and nav title are properly translated

[claude]

CLAUDE.md violation: The changelog entry for this PR should be placed at the top of the ### Changed section, above the #863 entry.

From CLAUDE.md: "ALWAYS place new entries at the top of their category section (newest first)"

Reference:

bitkit-android/CHANGELOG.md

Lines 24 to 28 in 4deca4e

	### Changed
	- Unified send flow with payment method switcher, details toggle, Lightning support for BIP21 payments, and improved fee rate defaults #863
	- Update external success screen title and image to match new design #883
	- Settings redesigned with tabbed navigation (General/Security/Advanced) with swipe support #857
	- Icons added to all settings rows for faster scanning #857

Suggested change

	- Unified send flow with payment method switcher, details toggle, Lightning support for BIP21 payments, and improved fee rate defaults #863
	- Update external success screen title and image to match new design #883
	- Unified send flow with payment method switcher, details toggle, Lightning support for BIP21 payments, and improved fee rate defaults #863