migrate orion repo into monorepo structure

go/migrations/000006_particle_tracking.up.sql

@@ -0,0 +1,21 @@
+-- Seen tracking: private per-user state
+CREATE TABLE particle_seen (
+    particle_id TEXT NOT NULL REFERENCES particles(id) ON DELETE CASCADE,
+    email VARCHAR(255) NOT NULL,
+    seen_at TIMESTAMPTZ NOT NULL DEFAULT NOW(),
+    PRIMARY KEY (particle_id, email)
+);
+
+-- Ack tracking: public, visible to others
+CREATE TABLE particle_acks (
+    particle_id TEXT NOT NULL REFERENCES particles(id) ON DELETE CASCADE,
+    email VARCHAR(255) NOT NULL,
+    acked_at TIMESTAMPTZ NOT NULL DEFAULT NOW(),
+    PRIMARY KEY (particle_id, email)
+);
+
+-- Index for bulk "which particles has this user seen?"
+CREATE INDEX idx_particle_seen_email ON particle_seen(email, particle_id);
+
+-- Index for "who acked this particle?"
+CREATE INDEX idx_particle_acks_particle ON particle_acks(particle_id);