feat: Replace Meetings with Calendar - events with types and assigned users

- Rename meetings table to events with type field (meeting/event)
- Add eventUsers junction table for user assignments
- Members see only events they're assigned to
- Calendar endpoint returns events + todos for month
- Add migration SQL for database changes

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

src/db/migrations/0001_meetings_to_events.sql

@@ -0,0 +1,21 @@
+-- Migration: Convert meetings to events with type and assigned users
+-- Run this migration manually or via drizzle-kit
+
+-- Step 1: Rename meetings table to events
+ALTER TABLE meetings RENAME TO events;
+
+-- Step 2: Add type column
+ALTER TABLE events ADD COLUMN type TEXT NOT NULL DEFAULT 'meeting';
+
+-- Step 3: Create event_users junction table
+CREATE TABLE event_users (
+  id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
+  event_id UUID NOT NULL REFERENCES events(id) ON DELETE CASCADE,
+  user_id UUID NOT NULL REFERENCES users(id) ON DELETE CASCADE,
+  assigned_at TIMESTAMP DEFAULT NOW() NOT NULL,
+  UNIQUE(event_id, user_id)
+);
+
+-- Step 4: Assign existing events to their creators
+INSERT INTO event_users (event_id, user_id)
+SELECT id, created_by FROM events WHERE created_by IS NOT NULL;