feat: add CPU and memory resource limits per app

- Add cpu_limit (REAL) and memory_limit (INTEGER) columns to apps table
  via migration 007
- Add CPULimit and MemoryLimit fields to App model with full CRUD support
- Add resource limits fields to app edit form with human-friendly
  memory input (e.g. 256m, 1g, 512k)
- Pass CPU and memory limits to Docker container creation via
  NanoCPUs and Memory host config fields
- Extract Docker container creation helpers (buildEnvSlice, buildMounts,
  buildResources) for cleaner code
- Add formatMemoryBytes template function for display
- Add comprehensive tests for parsing, formatting, model persistence,
  and container options

templates/app_edit.html

@@ -114,6 +114,38 @@
                 >
             </div>
 
+            <hr class="border-gray-200">
+
+            <h3 class="text-lg font-medium text-gray-900">Resource Limits</h3>
+
+            <div class="grid grid-cols-2 gap-4">
+                <div class="form-group">
+                    <label for="cpu_limit" class="label">CPU Limit (cores)</label>
+                    <input
+                        type="text"
+                        id="cpu_limit"
+                        name="cpu_limit"
+                        value="{{if .App.CPULimit.Valid}}{{.App.CPULimit.Float64}}{{end}}"
+                        class="input"
+                        placeholder="e.g. 0.5, 1, 2"
+                    >
+                    <p class="text-sm text-gray-500 mt-1">Number of CPU cores (e.g. 0.5 = half a core)</p>
+                </div>
+
+                <div class="form-group">
+                    <label for="memory_limit" class="label">Memory Limit</label>
+                    <input
+                        type="text"
+                        id="memory_limit"
+                        name="memory_limit"
+                        value="{{if .App.MemoryLimit.Valid}}{{formatMemoryBytes .App.MemoryLimit.Int64}}{{end}}"
+                        class="input"
+                        placeholder="e.g. 256m, 1g"
+                    >
+                    <p class="text-sm text-gray-500 mt-1">Memory with unit suffix (k, m, g) or plain bytes</p>
+                </div>
+            </div>
+
             <div class="flex justify-end gap-3 pt-4">
                 <a href="/apps/{{.App.ID}}" class="btn-secondary">Cancel</a>
                 <button type="submit" class="btn-primary">Save Changes</button>