Implement cached collector architecture with configurable timeouts

Major architectural refactor to eliminate false "host offline" alerts:

- Replace sequential blocking collectors with independent async tasks
- Each collector runs at configurable interval and updates shared cache
- ZMQ sender reads cache every 1-2s regardless of collector speed
- Collector intervals: CPU/Memory (1-10s), Backup/NixOS (30-60s), Disk/Systemd (60-300s)

All intervals now configurable via NixOS config:
- collectors.*.interval_seconds (collection frequency per collector)
- collectors.*.command_timeout_seconds (timeout for shell commands)
- notifications.check_interval_seconds (status change detection rate)

Command timeouts increased from hardcoded 2-3s to configurable 10-30s:
- Disk collector: 30s (SMART operations, lsblk)
- Systemd collector: 15s (systemctl, docker, du commands)
- Network collector: 10s (ip route, ip addr)

Benefits:
- No false "offline" alerts when slow collectors take >10s
- Different update rates for different metric types
- Better resource management with longer timeouts
- Full NixOS configuration control

Bump version to v0.1.193

CLAUDE.md

@@ -156,7 +156,7 @@ Complete migration from string-based metrics to structured JSON data. Eliminates
 - ✅ Backward compatibility via bridge conversion to existing UI widgets
 - ✅ All string parsing bugs eliminated
 
-### Cached Collector Architecture (🚧 PLANNED)
+### Cached Collector Architecture (✅ IMPLEMENTED)
 
 **Problem:** Blocking collectors prevent timely ZMQ transmission, causing false "host offline" alerts.
 
@@ -199,12 +199,42 @@ Every 1 second:
 - ✅ System stays responsive even with slow operations
 - ✅ Slow collectors can use longer timeouts without blocking
 
-**Implementation:**
-- Shared `AgentData` cache wrapped in `Arc<RwLock<>>`
-- Each collector spawned as independent tokio task
-- Collectors update their section of cache at their own rate
-- ZMQ sender reads cache every 1s and transmits
-- Stale data acceptable for slow-changing metrics (disk usage, SMART)
+**Implementation Details:**
+- **Shared cache**: `Arc<RwLock<AgentData>>` initialized at agent startup
+- **Collector intervals**: Fully configurable via NixOS config (`interval_seconds` per collector)
+  - Recommended: Fast (1-10s): CPU, Memory, Network
+  - Recommended: Medium (30-60s): Backup, NixOS
+  - Recommended: Slow (60-300s): Disk, Systemd
+- **Independent tasks**: Each collector spawned as separate tokio task in `Agent::new()`
+- **Cache updates**: Collectors acquire write lock → update → release immediately
+- **ZMQ sender**: Main loop reads cache every `collection_interval_seconds` and broadcasts
+- **Notification check**: Runs every `notifications.check_interval_seconds`
+- **Lock strategy**: Short-lived write locks prevent blocking, read locks for transmission
+- **Stale data**: Acceptable for slow-changing metrics (SMART data, disk usage)
+
+**Configuration (NixOS):**
+All intervals and timeouts configurable in `services/cm-dashboard.nix`:
+
+Collection Intervals:
+- `collectors.cpu.interval_seconds` (default: 10s)
+- `collectors.memory.interval_seconds` (default: 2s)
+- `collectors.disk.interval_seconds` (default: 300s)
+- `collectors.systemd.interval_seconds` (default: 10s)
+- `collectors.backup.interval_seconds` (default: 60s)
+- `collectors.network.interval_seconds` (default: 10s)
+- `collectors.nixos.interval_seconds` (default: 60s)
+- `notifications.check_interval_seconds` (default: 30s)
+- `collection_interval_seconds` - ZMQ transmission rate (default: 2s)
+
+Command Timeouts (prevent resource leaks from hung commands):
+- `collectors.disk.command_timeout_seconds` (default: 30s) - lsblk, smartctl, etc.
+- `collectors.systemd.command_timeout_seconds` (default: 15s) - systemctl, docker, du
+- `collectors.network.command_timeout_seconds` (default: 10s) - ip route, ip addr
+
+**Code Locations:**
+- agent/src/agent.rs:59-133 - Collector task spawning
+- agent/src/agent.rs:151-179 - Independent collector task runner
+- agent/src/agent.rs:199-207 - ZMQ sender in main loop
 
 ### Maintenance Mode