fix(questtracker): contain Blizzard quest icons within background

[0x963D]

What does this PR do?

Extends the addon-owned Quest Tracker background and divider far enough left to contain Blizzard's native quest icons when Show Quest Icons is enabled. Icon-disabled layouts keep the existing compact offset.

The right edge and tracker content alignment are unchanged. No Blizzard-owned frame or icon is modified.

Fixes #1197

How was it tested?

• Retail 12.0.7.68974 on Lillydan-Thunderhorn: populated tracker with native icons, reload, and world map open/close.
• 12.1 PTR 12.1.0.69111 on Lillydan-Anasterian: matched baseline/patched A/B, native icons enabled and disabled, and repeated reloads.
• taintLog 2: zero Quest Tracker / Objective Tracker matches on both clients after the tested interactions.
• Lua 5.1 parse with luac5.1 -p, ASCII scan, and git diff --check.
• Static audit confirms every relevant background/divider TOPLEFT anchor uses the shared offset, with no new events, hooks, frames, timers, polling, or allocations.

Not exercised because the available characters did not have those states ready: an empty tracker, a newly completed quest transition, live combat, and a new supertrack transition.

Screenshots

Matched 3440x1440 PTR captures at the same tracker position and UI scale:

Before	After

Checklist

• New settings default OFF (no behavior change without opt-in) - N/A; no new setting.
• Zero cost while disabled: no events registered, no polling, no hooks doing work, no frames built
• Cheap while enabled: event-driven (no polling, no timer-based logic, no per-frame allocations)
• No writes onto Blizzard-owned frames (weak-table pattern used); HookScript/hooksecurefunc only, never SetScript on Blizzard frames
• Tested in-game, works on live retail; no load errors on the 12.1 PTR client