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>

src/web/public/upload.html

@@ -2,7 +2,7 @@
 <html lang="en"><head>
 <meta charset="utf-8">
 <meta name="viewport" content="width=device-width, initial-scale=1.0, maximum-scale=1.0, user-scalable=no, viewport-fit=cover">
-<title>Upload Screenshot - Claudeman</title>
+<title>Upload Screenshot - Codeman</title>
 <style>
   * { box-sizing: border-box; margin: 0; padding: 0; }
   body {
@@ -49,7 +49,7 @@
 </style>
 </head><body>
 <div class="container">
-  <a class="back" href="/">&larr; Back to Claudeman</a>
+  <a class="back" href="/">&larr; Back to Codeman</a>
   <h1>Upload Screenshot</h1>
   <div class="drop-zone" id="drop">
     <p>Tap to select image</p>