Add infrastructure changelog system to task-mcp

Implements session-aware infrastructure change tracking for CF-179.

Changes:
- New changelog.ts with 3 MCP tools:
  - changelog_add: Add infrastructure changes
  - changelog_since_session: Query changes since last session
  - changelog_list: Time-based fallback query
- Integrated with session-start command via MCP
- Database-first architecture (PostgreSQL on infra VM)
- Session-relative queries (not fixed time windows)

Database schema:
- infrastructure_changelog table (6 fields)
- Migrated 5 historical changes
- Indexes on date, session_id, created_at

Task: CF-179

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

src/index.ts

@@ -26,6 +26,7 @@ import { taskDelegations, taskDelegationQuery } from './tools/delegations.js';
 import { projectLock, projectUnlock, projectLockStatus, projectContext } from './tools/locks.js';
 import { versionAdd, versionList, versionShow, versionUpdate, versionRelease, versionAssignTask } from './tools/versions.js';
 import { taskCommitAdd, taskCommitRemove, taskCommitsList, taskLinkCommits, sessionTasks } from './tools/commits.js';
+import { changelogAdd, changelogSinceSession, changelogList } from './tools/changelog.js';
 import {
   componentRegister,
   componentList,
@@ -287,6 +288,17 @@ server.setRequestHandler(CallToolRequestSchema, async (request) => {
         });
         break;
 
+      // Infrastructure Changelog
+      case 'changelog_add':
+        result = await changelogAdd(a as any);
+        break;
+      case 'changelog_since_session':
+        result = await changelogSinceSession(a as any);
+        break;
+      case 'changelog_list':
+        result = await changelogList(a.days_back, a.limit);
+        break;
+
       // Impact Analysis
       case 'component_register':
         result = JSON.stringify(await componentRegister(a.id, a.name, a.type, {