feat(phase5): calendar channels - events, RSVPs, calendar view

internal/db/db.go

@@ -380,6 +380,34 @@ CREATE TABLE IF NOT EXISTS blocks (
 CREATE INDEX IF NOT EXISTS idx_blocks_blocker ON blocks(blocker_id);
 CREATE INDEX IF NOT EXISTS idx_blocks_blocked ON blocks(blocked_id);
 
+-- Calendar events
+CREATE TABLE IF NOT EXISTS events (
+	id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
+	channel_id UUID NOT NULL REFERENCES channels(id) ON DELETE CASCADE,
+	creator_id UUID NOT NULL REFERENCES users(id) ON DELETE CASCADE,
+	title VARCHAR(255) NOT NULL,
+	description TEXT,
+	start_time TIMESTAMPTZ NOT NULL,
+	end_time TIMESTAMPTZ,
+	recurrence_rule VARCHAR(255),
+	location VARCHAR(255),
+	color VARCHAR(7),
+	created_at TIMESTAMPTZ NOT NULL DEFAULT NOW(),
+	updated_at TIMESTAMPTZ NOT NULL DEFAULT NOW()
+);
+
+CREATE INDEX IF NOT EXISTS idx_events_channel_time ON events(channel_id, start_time);
+
+CREATE TABLE IF NOT EXISTS event_rsvps (
+	event_id UUID NOT NULL REFERENCES events(id) ON DELETE CASCADE,
+	user_id UUID NOT NULL REFERENCES users(id) ON DELETE CASCADE,
+	status VARCHAR(16) NOT NULL CHECK (status IN ('going', 'maybe', 'no')),
+	responded_at TIMESTAMPTZ NOT NULL DEFAULT NOW(),
+	PRIMARY KEY (event_id, user_id)
+);
+
+CREATE INDEX IF NOT EXISTS idx_event_rsvps_event ON event_rsvps(event_id);
+
 -- Message full-text search
 ALTER TABLE messages ADD COLUMN IF NOT EXISTS search_vector tsvector;
 CREATE INDEX IF NOT EXISTS idx_messages_search ON messages USING GIN(search_vector);