refactor: Restructure monorepo to apps/server/ and apps/web/ layout

Move src/ → apps/server/ and packages/web/ → apps/web/ to adopt
standard monorepo conventions (apps/ for runnable apps, packages/
for reusable libraries). Update all config files, shared package
imports, test fixtures, and documentation to reflect new paths.

Key fixes:
- Update workspace config to ["apps/*", "packages/*"]
- Update tsconfig.json rootDir/include for apps/server/
- Add apps/web/** to vitest exclude list
- Update drizzle.config.ts schema path
- Fix ensure-schema.ts migration path detection (3 levels up in dev,
  2 levels up in dist)
- Fix tests/integration/cli-server.test.ts import paths
- Update packages/shared imports to apps/server/ paths
- Update all docs/ files with new paths

apps/server/db/repositories/change-set-repository.ts

@@ -0,0 +1,36 @@
+/**
+ * Change Set Repository Port Interface
+ *
+ * Port for ChangeSet aggregate operations.
+ * Implementations (Drizzle, etc.) are adapters.
+ */
+
+import type { ChangeSet, ChangeSetEntry } from '../schema.js';
+
+export type CreateChangeSetData = {
+  agentId: string | null;
+  agentName: string;
+  initiativeId: string;
+  mode: 'plan' | 'detail' | 'refine';
+  summary?: string | null;
+};
+
+export type CreateChangeSetEntryData = {
+  entityType: 'page' | 'phase' | 'task' | 'phase_dependency';
+  entityId: string;
+  action: 'create' | 'update' | 'delete';
+  previousState?: string | null;
+  newState?: string | null;
+  sortOrder?: number;
+};
+
+export type ChangeSetWithEntries = ChangeSet & { entries: ChangeSetEntry[] };
+
+export interface ChangeSetRepository {
+  createWithEntries(data: CreateChangeSetData, entries: CreateChangeSetEntryData[]): Promise<ChangeSet>;
+  findById(id: string): Promise<ChangeSet | null>;
+  findByIdWithEntries(id: string): Promise<ChangeSetWithEntries | null>;
+  findByInitiativeId(initiativeId: string): Promise<ChangeSet[]>;
+  findByAgentId(agentId: string): Promise<ChangeSet[]>;
+  markReverted(id: string): Promise<ChangeSet>;
+}