Restructure documentation into separate files with links

docs/USAGE.md

@@ -0,0 +1,96 @@
+# Usage Guide
+
+## Dashboard
+
+The main dashboard provides a real-time overview of all monitored resources with their current status, uptime, and response times.
+
+## History Page
+
+The **History** page displays detailed check data for all monitored resources with interactive graphs and performance metrics.
+
+### Time Window Selection
+
+- **7 Days** - Default view, showing hourly averages (168 data points)
+- **14 Days** - Shows 3-hourly averages (112 data points)
+- **30 Days** - Shows 6-hourly averages (120 data points)
+
+### Show Averages Toggle
+
+The **"Show Averages"** checkbox controls how data is displayed:
+
+#### When Enabled (Default)
+- Data is **bucketed and averaged** server-side
+- 7 Days: 1-hour buckets (168 points)
+- 14 Days: 3-hour buckets (112 points)
+- 30 Days: 6-hour buckets (120 points)
+- **Benefit**: Much faster page load, cleaner graphs with averaged response times
+- **Use when**: Viewing trends over time
+
+#### When Disabled
+- Shows up to 600 **raw individual checks** within the selected time window
+- **Benefit**: See exact check-by-check performance, spot patterns
+- **Use when**: Debugging specific issues, investigating downtime events
+
+### Graph Display
+
+Each resource shows:
+- **Response Time (Blue Line)** - Average response time in milliseconds
+- **Status Bars (Green/Red)** - 
+  - 🟢 Green = Resource was UP during that period
+  - 🔴 Red = Resource was DOWN during that period
+
+### Statistics
+
+Below each graph:
+- **Total Checks** - Number of checks performed in the time window
+- **Uptime %** - Percentage of checks that were successful (green = higher is better)
+- **Avg Response** - Average response time in milliseconds
+- **Successful Checks** - Count of successful vs total checks (e.g., 5592/5593)
+
+### Performance Notes
+
+- **Averaged mode** is optimized for performance and uses server-side aggregation
+- **Non-averaged mode** can be slower with large datasets (>600 checks)
+- Cache is updated every 2 minutes for averaged data
+- Each time window (7/14/30 days) has separate cache entries
+
+## Settings Page
+
+Configure global monitoring settings and notifications.
+
+### Email Notifications
+
+1. Toggle "Email Notifications" on
+2. Select your email provider (Gmail, Outlook, Yahoo, or Custom)
+3. Enter your email credentials
+4. **For Gmail**: Use an App Password (see instructions in the UI)
+5. Click "Send Test Email" to verify
+
+### Webhook Notifications
+
+1. Toggle "Webhook Notifications" on
+2. Enter your webhook URL (Slack, Discord, etc.)
+3. Click "Send Test Webhook" to verify
+
+### Other Settings
+
+- Timezone configuration
+- Data retention period
+- Alert thresholds
+- SLA targets
+
+## Adding Resources
+
+1. Click "Add Resource" on the dashboard
+2. Enter resource details:
+   - **Name**: Friendly name (e.g., "ZimaOS Home Server")
+   - **URL**: Full URL to monitor (e.g., "https://your-zima.example.com")
+   - **Check Interval**: How often to check (in milliseconds)
+   - **Timeout**: Maximum time to wait for response
+   - **Email To**: Email address for alerts (resource-specific)
+   - **HTTP Keyword**: Optional keyword to search for in response
+   - **SLA Target**: Target uptime percentage for this resource
+
+## SLA Report
+
+View Service Level Agreement compliance for all resources over configurable time periods.