Link support codes to agent sessions

- Server: Accept support_code param in WebSocket connection
- Server: Link code to session when agent connects, mark as connected
- Server: Mark code as completed when agent disconnects
- Agent: Accept support code from command line argument
- Agent: Send hostname and support_code in WebSocket params
- Portal: Trigger agent download with code in filename
- Portal: Show code reminder in download instructions
- Dashboard: Add machines list fetching (Access tab)
- Add TODO.md for feature tracking

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

agent/src/config.rs

@@ -21,6 +21,10 @@ pub struct Config {
     /// Optional hostname override
     pub hostname_override: Option<String>,
 
+    /// Support code for one-time support sessions (set via command line)
+    #[serde(skip)]
+    pub support_code: Option<String>,
+
     /// Capture settings
     #[serde(default)]
     pub capture: CaptureConfig,
@@ -119,6 +123,9 @@ impl Config {
                 let _ = config.save();
             }
 
+            // support_code is always None when loading from file (set via CLI)
+            config.support_code = None;
+
             return Ok(config);
         }
 
@@ -137,6 +144,7 @@ impl Config {
             api_key,
             agent_id,
             hostname_override: std::env::var("GURUCONNECT_HOSTNAME").ok(),
+            support_code: None, // Set via CLI
             capture: CaptureConfig::default(),
             encoding: EncodingConfig::default(),
         };