docs: update handbook What's coming next with missing features

docs/HANDBOOK.md

@@ -1,6 +1,6 @@
 # Darkwatch Handbook
 
-**Last updated:** 2026-04-11
+**Last updated:** 2026-04-12
 
 A reference for everyone working on or with Darkwatch — whether you're a DM discovering the tool, a developer joining the project, or a collaborator adding features.
 
@@ -116,8 +116,12 @@ Features currently planned or in progress:
 - **Per-enemy dice rolls** — DM triggers attack/damage rolls from individual enemies in the tracker
 - **Party loot / shared inventory** — campaign-level shared item pool, DM-managed
 - **Creature gallery / NPC system** — saved enemy stat blocks, quick-add to initiative tracker
+- **Initiative enhancements** — turn timer per combatant, re-roll initiative mid-combat, individual initiative mode (each combatant rolls separately, as opposed to team-based; needed for non-Shadowdark systems)
+- **Google / social login** — OAuth alongside the existing email/password flow
+- **Snow atmosphere effect** — tsParticles, evaluating after DM feedback on existing effects
+- **Ambient audio** — optional background sound; low priority
 
-Longer-term ideas: multi-system support (Cairn, Knave, Cyberpunk RED), metrics and analytics, API documentation, and a public marketing site.
+Longer-term ideas: multi-system support (Cairn, Knave, Cyberpunk RED), profile image uploads, metrics and analytics, API documentation, and a public marketing site.
 
 ## Known limitations
 
@@ -307,3 +311,5 @@ We use a structured approach: **brainstorm → spec → plan → implement**.
 All specs and plans are committed to the repo. Check `docs/superpowers/` to understand why things were built the way they were.
 
 **Project-local Claude skills** live in `.claude/skills/`. See `CLAUDE.md` for the list of available skills and how to invoke them.
+
+**Technical backlog** (DB migration tooling, containerization, Kubernetes, metrics infrastructure) is tracked in `docs/ROADMAP.md`.