feat(auth): merge mobile+email logins into one account via BizGaze person-id (#2)

Provisioning now keys the Biz Connect account on bz.bizgazeUserId (the same
value whether the person signs in with email or mobile) instead of the typed
identifier, so both logins resolve to a single contact. Legacy rows get the
person-id stamped on next login; an existing duplicate created under the same
identifier is folded in via a transactional users.mergeInto() that reassigns
all messages/memberships/reactions/votes/favorites/ownership to the survivor.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

brand-assets/README-for-VSClaude.md

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+# Biz Connect — master assets for VS Claude
+
+Three masters, exactly as requested. Regenerate/wire everything from these.
+
+## 1. App icon  →  app-icon-1024.png
+- 1024×1024, full-bleed solid brand-blue square (no baked-in rounded corners), C mark
+  centred with safe padding. Use as the single source to regenerate:
+  Windows `.ico` (multi-size — fixes the tiny/blurry taskbar icon), PWA icons
+  (192, 512, maskable), apple-touch-icon, favicon, and the Android/iOS mobile icons.
+
+## 2. Splash  →  splash-2732-dark.png  (primary)  ·  splash-2732-light.png (optional)
+- 2732×2732. Dark = brand blue (use this everywhere by default). Light = white background
+  variant if you support a light theme. Use for the desktop/web launch and the mobile
+  native splash. (Native launch screens should stay static — no animation.)
+
+## 3. Loader  →  animated SVG (pick per context)
+- loader-ring.svg        default everyday spinner, for LIGHT backgrounds (blue track + yellow arc)
+- loader-orbit.svg       branded spinner (the C with a circling dot), LIGHT backgrounds
+- loader-orbit-dark.svg  same branded spinner for DARK/overlay backgrounds (white C)
+Recommended: use loader-ring.svg as the standard "Loading…" and in-app spinner; use
+loader-orbit(-dark).svg for the hero "Connecting…" moment. SVG is animated, tiny, scalable.
+
+## Brand
+Blue #1F3B73  ·  Blue-dark #16294F  ·  Yellow #FFC708  ·  (deeper gold #E0AC00 for "Connect" on white)