chore: rename Claudeman to Codeman

Full product rename across 109 files (~834 occurrences):
- Env vars: CLAUDEMAN_* → CODEMAN_*
- Data dirs: ~/.claudeman/ → ~/.codeman/, ~/claudeman-cases/ → ~/codeman-cases/
- tmux prefix: claudeman- → codeman-
- localStorage: claudeman-* → codeman-*
- Package/CLI: claudeman → codeman
- GitHub repo: Ark0N/Claudeman → Ark0N/Codeman
- systemd service: claudeman-web → codeman-web
- Class: ClaudemanApp → CodemanApp

Migration infrastructure for seamless transition:
- state-store.ts: auto-migrates data directories on startup
- tmux-manager.ts: dual-prefix detection (legacy claudeman- sessions)
- app.js: localStorage key migration (preserves old keys)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

test/api-responses.test.ts

@@ -537,7 +537,7 @@ describe('API Response Structures', () => {
     it('should validate case info', () => {
       const caseInfo: CaseInfo = {
         name: 'my-project',
-        path: '/home/user/claudeman-cases/my-project',
+        path: '/home/user/codeman-cases/my-project',
         hasClaudeMd: true,
       };
 
@@ -549,7 +549,7 @@ describe('API Response Structures', () => {
     it('should handle optional hasClaudeMd', () => {
       const caseInfo: CaseInfo = {
         name: 'new-project',
-        path: '/home/user/claudeman-cases/new-project',
+        path: '/home/user/codeman-cases/new-project',
       };
 
       expect(caseInfo.hasClaudeMd).toBeUndefined();