bump CAPI min to 1.12.4

Replace the hardcoded knownTrackingSpells class table and the
icon-substring spellbook scan with ClassicAPI's native tracking
functions:

- RefreshSpells now enumerates GetNumTrackingTypes() / GetTrackingInfo(),
  which the DLL derives from the spellbook by tracking-aura effect. This
  drops the per-class spell/icon table and picks up server-custom
  trackers (e.g. Turtle's Find Trees) automatically.
- Selecting a tracker in the menu uses SetTracking(index) instead of
  CastSpell(slot, BOOKTYPE_SPELL).
- Keep the Druid Cat Form gate on Track Humanoids (5225) and the
  existing invalidSpells filter. Falls back to no entries if the tracking
  API is absent.

Active icon (GetTrackingTexture), cancel (CancelTrackingBuff), and the
hover tooltip (GameTooltip:SetTrackingSpell) were already native and are
unchanged.

pfUI.lua

@@ -86,13 +86,14 @@ do
   end
 end
 
-pfUI_playerDB = pfUI_playerDB or {}
-pfUI_config = pfUI_config or {}
-pfUI_init = pfUI_init or {}
-pfUI_profiles = pfUI_profiles or {}
-pfUI_addon_profiles = pfUI_addon_profiles or {}
-pfUI_cache = pfUI_cache or {}
-pfUI_throttle = pfUI_throttle or {}
+-- initialize saved variables
+pfUI_playerDB = {}
+pfUI_config = {}
+pfUI_init = {}
+pfUI_profiles = {}
+pfUI_addon_profiles = {}
+pfUI_cache = {}
+pfUI_throttle = {}
 
 -- localization
 pfUI_locale = {}