Phase 3: Session recording/playback and encrypted profile export/import

Session Recording & Playback:
- Add recording package with asciicast v2 format writer and reader
- Recorder captures terminal I/O with timestamps from SSH and Telnet sessions
- Input and output events recorded via hooks in session manager callbacks
- Recording store manages .cast files in ~/Library/Application Support/NexusTerminal/recordings
- Recording browser modal lists all saved recordings with metadata
- Full playback viewer with embedded xterm.js terminal, progress scrubber,
  play/pause/restart controls, and 0.5x-10x speed adjustment
- Recording indicator (pulsing red dot) shown on active tab during capture
- Keyboard shortcut Cmd+Shift+R to toggle recording on active session
- Tests for recording, store listing, deletion, and double-close safety

Encrypted Profile Export/Import:
- Add exportimport package with AES-256-GCM encryption (Argon2id key derivation)
- File format: version byte + 32-byte salt + 12-byte nonce + ciphertext
- Same Argon2id parameters as vault (128 MiB, 3 iterations, 4 threads)
- Export modal with profile selection checkboxes and password entry
- Import modal with password entry and conflict strategy (skip/overwrite/duplicate)
- Native save/open file dialogs for .nexus files
- Tests for round-trip encryption, wrong password rejection, corrupt files
- Replaced placeholder import/export with full encrypted implementation

UI:
- Added export and recordings buttons to sidebar footer
- Recording and playback CSS with charcoal design tokens
- Wired RecordingManager and ExportImportUI into app.js

frontend/wailsjs/go/api/Service.js

@@ -34,6 +34,10 @@ export function DeleteProfileSecrets(arg1) {
   return window['go']['api']['Service']['DeleteProfileSecrets'](arg1);
 }
 
+export function DeleteRecording(arg1) {
+  return window['go']['api']['Service']['DeleteRecording'](arg1);
+}
+
 export function DisconnectSession(arg1) {
   return window['go']['api']['Service']['DisconnectSession'](arg1);
 }
@@ -46,6 +50,10 @@ export function ExportProfiles(arg1) {
   return window['go']['api']['Service']['ExportProfiles'](arg1);
 }
 
+export function ExportProfilesEncrypted(arg1, arg2) {
+  return window['go']['api']['Service']['ExportProfilesEncrypted'](arg1, arg2);
+}
+
 export function GetAppInfo() {
   return window['go']['api']['Service']['GetAppInfo']();
 }
@@ -58,6 +66,10 @@ export function GetProfile(arg1) {
   return window['go']['api']['Service']['GetProfile'](arg1);
 }
 
+export function GetRecording(arg1) {
+  return window['go']['api']['Service']['GetRecording'](arg1);
+}
+
 export function GetSessionHistory(arg1) {
   return window['go']['api']['Service']['GetSessionHistory'](arg1);
 }
@@ -66,10 +78,18 @@ export function ImportProfiles(arg1, arg2) {
   return window['go']['api']['Service']['ImportProfiles'](arg1, arg2);
 }
 
+export function ImportProfilesEncrypted(arg1, arg2) {
+  return window['go']['api']['Service']['ImportProfilesEncrypted'](arg1, arg2);
+}
+
 export function InitialiseSecretStore(arg1) {
   return window['go']['api']['Service']['InitialiseSecretStore'](arg1);
 }
 
+export function IsRecording(arg1) {
+  return window['go']['api']['Service']['IsRecording'](arg1);
+}
+
 export function IsSecretStoreInitialised() {
   return window['go']['api']['Service']['IsSecretStoreInitialised']();
 }
@@ -110,6 +130,10 @@ export function ListProfilesByTag(arg1) {
   return window['go']['api']['Service']['ListProfilesByTag'](arg1);
 }
 
+export function ListRecordings() {
+  return window['go']['api']['Service']['ListRecordings']();
+}
+
 export function ListSessions() {
   return window['go']['api']['Service']['ListSessions']();
 }
@@ -186,10 +210,18 @@ export function StartPortForward(arg1, arg2) {
   return window['go']['api']['Service']['StartPortForward'](arg1, arg2);
 }
 
+export function StartRecording(arg1, arg2, arg3) {
+  return window['go']['api']['Service']['StartRecording'](arg1, arg2, arg3);
+}
+
 export function StopPortForward(arg1, arg2) {
   return window['go']['api']['Service']['StopPortForward'](arg1, arg2);
 }
 
+export function StopRecording(arg1) {
+  return window['go']['api']['Service']['StopRecording'](arg1);
+}
+
 export function TestConnection(arg1, arg2) {
   return window['go']['api']['Service']['TestConnection'](arg1, arg2);
 }