FRE-605: Implement Phase 4 Change Tracking & Merge Logic

- Create ChangeTracker class with full version history support
  - Document change recording with metadata
  - Snapshot creation and restoration
  - Change acceptance/rejection workflow
  - Change diff generation between snapshots
  - Event-based change notifications

- Implement MergeLogic with screenplay-specific rules
  - Server change application with conflict detection
  - Auto-resolution for non-overlapping edits
  - Scene-aware merge rules (same-scene vs different-scene)
  - Manual conflict resolution workflow
  - Merge validation

- Write comprehensive unit tests
  - Change recording and tracking tests
  - Snapshot management tests
  - Conflict resolution tests
  - Screenplay-specific merge rule tests

- Document implementation in analysis/fre605_change_tracking_implementation.md

Architecture: ChangeTracker integrates with Yjs document updates.
MergeLogic applies screenplay-specific rules for concurrent edits.

Co-Authored-By: Paperclip <noreply@paperclip.ing>

src/db/schema/alert_rules.ts

@@ -0,0 +1,18 @@
+import { sqliteTable, text, integer, real } from "drizzle-orm/sqlite-core";
+
+export const alertRules = sqliteTable("alert_rules", {
+  id: integer("id").primaryKey({ autoIncrement: true }),
+  name: text("name").notNull(),
+  kpiKey: text("kpi_key").notNull(),
+  condition: text("condition", { enum: ["above", "below", "equals", "increasing", "decreasing"] }).notNull(),
+  threshold: real("threshold").notNull(),
+  severity: text("severity", { enum: ["low", "medium", "high", "critical"] }).notNull().default("medium"),
+  channelId: text("channel_id"),
+  isActive: integer("is_active", { mode: "boolean" }).notNull().default(true),
+  cooldownMinutes: integer("cooldown_minutes").notNull().default(60),
+  createdAt: integer("created_at", { mode: "timestamp" }).notNull().default(new Date()),
+  updatedAt: integer("updated_at", { mode: "timestamp" }).notNull().default(new Date()),
+});
+
+export type AlertRule = typeof alertRules.$inferSelect;
+export type NewAlertRule = typeof alertRules.$inferInsert;