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.d.ts

@@ -19,24 +19,34 @@ export function DeleteProfile(arg1:string):Promise<void>;
 
 export function DeleteProfileSecrets(arg1:string):Promise<void>;
 
+export function DeleteRecording(arg1:string):Promise<void>;
+
 export function DisconnectSession(arg1:string):Promise<void>;
 
 export function DuplicateProfile(arg1:string):Promise<models.Profile>;
 
 export function ExportProfiles(arg1:boolean):Promise<string>;
 
+export function ExportProfilesEncrypted(arg1:Array<string>,arg2:string):Promise<string>;
+
 export function GetAppInfo():Promise<Record<string, string>>;
 
 export function GetPreferences():Promise<models.AppPreferences>;
 
 export function GetProfile(arg1:string):Promise<models.Profile>;
 
+export function GetRecording(arg1:string):Promise<Record<string, any>>;
+
 export function GetSessionHistory(arg1:string):Promise<Array<Record<string, any>>>;
 
 export function ImportProfiles(arg1:string,arg2:string):Promise<number>;
 
+export function ImportProfilesEncrypted(arg1:string,arg2:string):Promise<number>;
+
 export function InitialiseSecretStore(arg1:string):Promise<void>;
 
+export function IsRecording(arg1:string):Promise<boolean>;
+
 export function IsSecretStoreInitialised():Promise<boolean>;
 
 export function IsSecretStoreUnlocked():Promise<boolean>;
@@ -57,6 +67,8 @@ export function ListProfilesByProtocol(arg1:string):Promise<Array<models.Profile
 
 export function ListProfilesByTag(arg1:string):Promise<Array<models.Profile>>;
 
+export function ListRecordings():Promise<Array<Record<string, any>>>;
+
 export function ListSessions():Promise<Array<models.SessionInfo>>;
 
 export function LockSecretStore():Promise<void>;
@@ -95,8 +107,12 @@ export function SetProfileSecret(arg1:string,arg2:string,arg3:string):Promise<vo
 
 export function StartPortForward(arg1:string,arg2:models.PortForward):Promise<void>;
 
+export function StartRecording(arg1:string,arg2:number,arg3:number):Promise<string>;
+
 export function StopPortForward(arg1:string,arg2:string):Promise<void>;
 
+export function StopRecording(arg1:string):Promise<void>;
+
 export function TestConnection(arg1:string,arg2:number):Promise<Record<string, any>>;
 
 export function UnlockSecretStore(arg1:string):Promise<void>;