refactor(context): Extract context modules from god object

- Create src/context/docker.js - Docker operations
- Create src/context/caddy.js - Caddyfile manipulation
- Create src/context/dns.js - DNS token management and API calls
- Create src/context/session.js - Session wrapper
- Create src/context/index.js - Context assembly (DI container)

Breaks up the 50+ property ctx god object into domain-specific modules

dashcaddy-api/src/context/session.js

@@ -0,0 +1,21 @@
+/**
+ * Session context - IP-based session management
+ * (Implementation provided by middleware, just re-exported here)
+ */
+
+function createSessionContext(middlewareResult) {
+  const { ipSessions, SESSION_DURATIONS, getClientIP, createIPSession, setSessionCookie, clearIPSession, clearSessionCookie, isSessionValid } = middlewareResult;
+
+  return {
+    ipSessions,
+    durations: SESSION_DURATIONS,
+    getClientIP,
+    create: createIPSession,
+    setCookie: setSessionCookie,
+    clear: clearIPSession,
+    clearCookie: clearSessionCookie,
+    isValid: isSessionValid,
+  };
+}
+
+module.exports = { createSessionContext };