fix(store): generate a unique id per Store instance

[LoboGuardian]

Problem

Store.__init__ defaults id to str(uuid4()):

def __init__(self, default={}, subscribe=True, id=str(uuid4())):

Default arguments are evaluated once, at import time, so every Store created without an explicit id receives the same UUID. Each then registers under that same key in SuperStore.stores (add() overwrites), so two independent default-constructed stores collapse into one endpoint — /api/_store/{id}/* traffic for store A is served by whichever store registered last.

Fix

Default id=None and generate the UUID inside __init__:

def __init__(self, default={}, subscribe=True, id=None):
    self._id = id if id is not None else str(uuid4())

Verification

a, b = Store(), Store()   -> a._id != b._id   ✓
Store(id="x")._id == "x"                        ✓

No API change; explicit ids still honored (incl. AuthStore, which passes id=self._id).

[Az107]

LGTM.
Setting base branch to develop