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).

api/core.lua

@@ -422,6 +422,16 @@ function SlashCmdList.MTH(msg, editbox)
 				MTH:Print("|cffaaffaaArmed.|r Open any vendor, trainer, or stable master to capture their ID.")
 			end
 		end
+	elseif lowerCmd == "dev" then
+		if lowerArg == "petmigrate" then
+			if type(MTH_CommandPetsMigrate) == "function" then
+				MTH_CommandPetsMigrate()
+			else
+				MTH:Print("Pet migration command unavailable.")
+			end
+		else
+			MTH:Print("Dev commands: /mth dev petmigrate")
+		end
 	elseif lowerCmd == "food" then
 		local sub = lowerArg
 		local function MTH_FoodItemLabel(itemId)