feat(agent): setup Cargo.toml et structure complète

Initialise la structure de l'agent Rust avec tous les modules stub :
config, payload, metrics (cpu/memory/disk/network/uptime/temperature/smart),
transport (udp/mqtt). Corrige les features sysinfo 0.30 (pas de feature
disk/networks séparées). Compile sans erreurs.

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

agent/src/metrics/cpu.rs

@@ -0,0 +1,3 @@
+pub fn get(_sys: &sysinfo::System) -> f32 {
+    0.0
+}

agent/src/metrics/disk.rs

@@ -0,0 +1,5 @@
+use sysinfo::Disks;
+
+pub fn get(_disks: &Disks) -> (u64, u64, u64) {
+    (0, 0, 0)
+}

agent/src/metrics/memory.rs

@@ -0,0 +1,3 @@
+pub fn get(_sys: &sysinfo::System) -> (u64, u64, u64) {
+    (0, 0, 0)
+}

agent/src/metrics/mod.rs

@@ -0,0 +1,7 @@
+pub mod cpu;
+pub mod disk;
+pub mod memory;
+pub mod network;
+pub mod smart;
+pub mod temperature;
+pub mod uptime;

agent/src/metrics/network.rs

@@ -0,0 +1,5 @@
+use sysinfo::Networks;
+
+pub fn get(_nets: &Networks) -> (u64, u64) {
+    (0, 0)
+}

agent/src/metrics/smart.rs

@@ -0,0 +1,13 @@
+use crate::payload::SmartMetrics;
+
+pub fn is_available() -> bool {
+    false
+}
+
+pub fn parse_json(_: &str) -> Result<SmartMetrics, serde_json::Error> {
+    serde_json::from_str("null")
+}
+
+pub fn collect() -> Option<SmartMetrics> {
+    None
+}

agent/src/metrics/temperature.rs

@@ -0,0 +1,5 @@
+use sysinfo::Components;
+
+pub fn get(_c: &Components) -> Option<f32> {
+    None
+}

agent/src/metrics/uptime.rs

@@ -0,0 +1,3 @@
+pub fn get() -> u64 {
+    0
+}