Add story-graph narrative system (campaigns, editors, runtime)

Introduce the narrative layer as a directed story-flow graph: an authored
campaign a player walks node by node, replacing the interim slot/chapter model.

Schema (migrations 015-021):
- mysteries, global NPC templates + named poses, per-user playthroughs
- story_nodes, terminals, utterances (the flow graph and dialogue trees)
- clean cutover: retire slot cutscenes/chapters/seen_dialogue

Runtime:
- New Game creates a playthrough bound to the JWT identity (dev test-user fallback)
- advance() walks the graph cutscene -> dialogue -> level -> ..., auto-skipping gates
- branching dialogue: player choices route out through node terminals

Admin authoring:
- NPC editor: upload named poses to the gupi MinIO bucket
- mystery graph editor: vertical node canvas, wiring, entrypoint, delete-by-click
- dialogue crafter: utterance tree, Tab to add child, 1/2 speaker, undo

Content authored via the manifest importer / admin panel and seeded for Glass
Harbour. MinIO added to the dev stack; dev container runs in development mode.

Also includes a folder-widget simplification (removes open/close) and a
resolveUserId auth helper.

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

migrations/016_dialogue_step_npc_cascade.sql

@@ -0,0 +1,7 @@
+-- A dialogue step is meaningless without its speaker. Cascade deletes from npcs
+-- so that removing an NPC (or dropping a whole mystery, which cascades to its
+-- cast) also removes the steps that reference it, rather than failing on the
+-- non-cascading foreign key.
+ALTER TABLE osint.dialogue_steps DROP CONSTRAINT dialogue_steps_npc_id_fkey;
+ALTER TABLE osint.dialogue_steps ADD CONSTRAINT dialogue_steps_npc_id_fkey
+  FOREIGN KEY (npc_id) REFERENCES osint.npcs(id) ON DELETE CASCADE;