feat: basic schedule

schema.sql

@@ -100,4 +100,25 @@ CREATE TABLE IF NOT EXISTS project_members (
     PRIMARY KEY (project_id, user_id)
 );
 
---
+--
+-- Scheduling (one-to-one sessions)
+--
+CREATE TABLE IF NOT EXISTS schedules (
+    id BIGSERIAL PRIMARY KEY,
+    guild_id BIGINT NOT NULL,
+    requester_id BIGINT NOT NULL,
+    invitee_id BIGINT NOT NULL,
+    scheduled_at TIMESTAMPTZ NOT NULL,
+    status TEXT NOT NULL DEFAULT 'pending', -- pending, accepted, declined, reschedule_requested
+    description TEXT,
+    reminder_sent BOOLEAN NOT NULL DEFAULT FALSE,
+    created_at TIMESTAMPTZ NOT NULL DEFAULT NOW()
+);
+
+CREATE TABLE IF NOT EXISTS schedule_messages (
+    schedule_id BIGINT NOT NULL REFERENCES schedules(id) ON DELETE CASCADE,
+    message_id BIGINT NOT NULL,
+    channel_id BIGINT NOT NULL,
+    is_dm BOOLEAN NOT NULL DEFAULT TRUE,
+    PRIMARY KEY (schedule_id, message_id)
+);