Add CRUD operations to session dialog

[Copilot]

The session dialog previously only supported selecting/switching between existing sessions. This PR adds full CRUD (Create, Read, Update, Delete) operations to allow users to manage sessions directly from the dialog interface.

Changes Made

New Key Bindings

• n - Create new session with custom title
• e - Edit selected session title
• d - Delete selected session (with confirmation)
• y - Confirm deletion in confirmation mode

Dialog Modes

Added support for multiple interaction modes:

• List mode - Browse and select sessions (default)
• Create mode - Input field for new session title
• Edit mode - Input field pre-filled with current session title
• Delete confirmation - Safety prompt before deletion

UI Improvements

• Updated dialog title from "Switch Session" to "Manage Sessions"
• Added contextual help text showing available operations
• Enhanced visual feedback with mode-specific layouts
• Integrated textinput component for title editing

Backend Integration

• Wired session dialog to use existing session service methods (Create, Save, Delete)
• Added new message types (SessionCreatedMsg, SessionUpdatedMsg, SessionDeletedMsg)
• Updated main TUI to handle CRUD messages and refresh session list automatically

Example Usage

┌──────────────────────────────────┐
│                                  │
│   Manage Sessions                │
│                                  │
│   ► Production Pentest           │
│     Development Tests            │
│     Client Demo                  │
│                                  │
│   n: new  e: edit  d: delete     │
│   enter: select  esc: close      │
│                                  │
└──────────────────────────────────┘

The implementation maintains consistency with existing dialog patterns while providing a seamless user experience for session management.

Fixes #21.

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[yyovil]

User should be able to delete multiple sessions and also a shortcut for deleting all of them.