Unify SavedVariables into two clean roots with one-time migration

Collapse all legacy/scattered SavedVariables from absorbed standalone
addons (FeedOMatic, ZHunter/zButtons, SmartAmmo, AutoQuest, AntiDaze,
AutoStrip, MinimapButton) into two persisted globals with clean per-module
nesting under .modules.<id>.

Migration engine (api/savedvariables.lua):
- MTH_SV_EnsureSchema() with schemaVersion gate, idempotent + non-destructive
- Per-module migrators map old locations -> canonical nested stores
- Driven by an ADDON_LOADED("MetaHunt") handler so it runs only AFTER WoW
  loads the real SavedVariables (fixes announce-every-session bug that ran
  the migration on empty pre-load defaults)
- One-time player-facing chat announce, gated on real legacy data present

Framework/config:
- core-framework InitSavedVariables no longer runs migration at file-load;
  unconditionally strips account-root module aliases
- config.lua stops re-creating root[module] aliases (was duplicating data
  onto disk); canonical store stays under .modules.<id>

Modules:
- feedomatic: bind FOM_* globals as runtime aliases into nested store,
  drop persisted duplicates and .legacy blob
- zhunter: ZHunterMod_Saved re-pointed at .modules.zhunter
- smartammo/autoquest/antidaze/autostrip/minimapbutton read nested store

TOC trimmed to MTH_SavedVariables + MTH_CharSavedVariables only.
Profiles unchanged (already snapshot/apply the nested .modules structure).

Also includes pet-scan refinements: canonical pet key derivation and
level-independent pet signature (schema v3).

modules/zhunter/module.lua

@@ -165,18 +165,11 @@ MTH_ZH_ApplyEnabledRuntimeState = function(source)
 end
 
 MTH_ZH_SyncSavedVariables = function()
-	if not MTH or not MTH.GetModuleCharSavedVariables then
-		return
-	end
-
-	local moduleStore = MTH:GetModuleCharSavedVariables("zhunter")
-
-	if type(ZHunterMod_Saved) == "table" then
-		if MTH_CharSavedVariables and MTH_CharSavedVariables.modules then
-			MTH_CharSavedVariables.modules.zhunter = ZHunterMod_Saved
-		end
-	elseif type(moduleStore) == "table" then
-		ZHunterMod_Saved = moduleStore
+	-- Bind the ZHunterMod_Saved global as a runtime alias into the canonical
+	-- nested store (MTH_CharSavedVariables.modules.zhunter). GetSavedRoot does the
+	-- adoption + aliasing; there is no second on-disk copy anymore.
+	if type(MTH_ZH_GetSavedRoot) == "function" then
+		MTH_ZH_GetSavedRoot()
 	end
 end