Add port mappings feature, update app icon, and enhance default instructions

- Add per-project port mapping configuration (host:container port pairs with
  TCP/UDP protocol) stored in project config and applied as Docker port
  bindings at container creation. Port changes trigger automatic container
  recreation via fingerprint detection.
- Create PortMappingsModal UI component following the same pattern as
  EnvVarsModal, integrated into ProjectCard config panel.
- Inject port mapping details into CLAUDE_INSTRUCTIONS so Claude inside the
  container knows which ports are available for testing services.
- Update default global instructions for new installs to encourage use of
  subagents for long-running and parallel tasks.
- Replace app icons with new v2 sun logo design for better visibility at
  small sizes (taskbar/dock).

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

app/src-tauri/src/models/project.rs

@@ -12,6 +12,18 @@ pub struct ProjectPath {
     pub mount_name: String,
 }
 
+#[derive(Debug, Clone, Serialize, Deserialize, PartialEq)]
+pub struct PortMapping {
+    pub host_port: u16,
+    pub container_port: u16,
+    #[serde(default = "default_protocol")]
+    pub protocol: String,
+}
+
+fn default_protocol() -> String {
+    "tcp".to_string()
+}
+
 #[derive(Debug, Clone, Serialize, Deserialize)]
 pub struct Project {
     pub id: String,
@@ -30,6 +42,8 @@ pub struct Project {
     #[serde(default)]
     pub custom_env_vars: Vec<EnvVar>,
     #[serde(default)]
+    pub port_mappings: Vec<PortMapping>,
+    #[serde(default)]
     pub claude_instructions: Option<String>,
     pub created_at: String,
     pub updated_at: String,
@@ -114,6 +128,7 @@ impl Project {
             git_user_name: None,
             git_user_email: None,
             custom_env_vars: Vec::new(),
+            port_mappings: Vec::new(),
             claude_instructions: None,
             created_at: now.clone(),
             updated_at: now,