refactor: migrate templates and static files to self-contained modules

Templates Migration:
- Migrate admin templates to modules (tenancy, billing, monitoring, marketplace, etc.)
- Migrate vendor templates to modules (tenancy, billing, orders, messaging, etc.)
- Migrate storefront templates to modules (catalog, customers, orders, cart, checkout, cms)
- Migrate public templates to modules (billing, marketplace, cms)
- Keep shared templates in app/templates/ (base.html, errors/, partials/, macros/)
- Migrate letzshop partials to marketplace module

Static Files Migration:
- Migrate admin JS to modules: tenancy (23 files), core (5 files), monitoring (1 file)
- Migrate vendor JS to modules: tenancy (4 files), core (2 files)
- Migrate shared JS: vendor-selector.js to core, media-picker.js to cms
- Migrate storefront JS: storefront-layout.js to core
- Keep framework JS in static/ (api-client, utils, money, icons, log-config, lib/)
- Update all template references to use module_static paths

Naming Consistency:
- Rename static/platform/ to static/public/
- Rename app/templates/platform/ to app/templates/public/
- Update all extends and static references

Documentation:
- Update module-system.md with shared templates documentation
- Update frontend-structure.md with new module JS organization

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

app/modules/monitoring/static/admin/js/platform-health.js

@@ -0,0 +1,129 @@
+// noqa: js-006 - async init pattern is safe, loadData has try/catch
+// static/admin/js/platform-health.js
+/**
+ * Admin platform health monitoring page logic
+ * Displays system metrics, capacity thresholds, and scaling recommendations
+ */
+
+const adminPlatformHealthLog = window.LogConfig.loggers.adminPlatformHealth ||
+    window.LogConfig.createLogger('adminPlatformHealth', false);
+
+adminPlatformHealthLog.info('Loading...');
+
+function adminPlatformHealth() {
+    adminPlatformHealthLog.info('adminPlatformHealth() called');
+
+    return {
+        // Inherit base layout state
+        ...data(),
+
+        // Set page identifier
+        currentPage: 'platform-health',
+
+        // Loading states
+        loading: true,
+        error: '',
+
+        // Health data
+        health: null,
+
+        // Auto-refresh interval (30 seconds)
+        refreshInterval: null,
+
+        async init() {
+            adminPlatformHealthLog.info('Platform Health init() called');
+
+            // Guard against multiple initialization
+            if (window._adminPlatformHealthInitialized) {
+                adminPlatformHealthLog.warn('Already initialized, skipping');
+                return;
+            }
+            window._adminPlatformHealthInitialized = true;
+
+            // Load initial data
+            await this.loadHealth();
+
+            // Set up auto-refresh every 30 seconds
+            this.refreshInterval = setInterval(() => {
+                this.loadHealth();
+            }, 30000);
+
+            adminPlatformHealthLog.info('Platform Health initialization complete');
+        },
+
+        /**
+         * Clean up on component destroy
+         */
+        destroy() {
+            if (this.refreshInterval) {
+                clearInterval(this.refreshInterval);
+                this.refreshInterval = null;
+            }
+        },
+
+        /**
+         * Load platform health data
+         */
+        async loadHealth() {
+            this.loading = true;
+            this.error = '';
+
+            try {
+                const response = await apiClient.get('/admin/platform/health');
+                this.health = response;
+
+                adminPlatformHealthLog.info('Loaded health data:', {
+                    status: response.overall_status,
+                    tier: response.infrastructure_tier
+                });
+            } catch (error) {
+                adminPlatformHealthLog.error('Failed to load health:', error);
+                this.error = error.message || 'Failed to load platform health';
+            } finally {
+                this.loading = false;
+            }
+        },
+
+        /**
+         * Manual refresh
+         */
+        async refresh() {
+            await this.loadHealth();
+        },
+
+        /**
+         * Format number with locale
+         */
+        formatNumber(num) {
+            if (num === null || num === undefined) return '0';
+            if (typeof num === 'number' && num % 1 !== 0) {
+                return num.toFixed(2);
+            }
+            return new Intl.NumberFormat('en-US').format(num);
+        },
+
+        /**
+         * Format storage size
+         */
+        formatStorage(gb) {
+            if (gb === null || gb === undefined) return '0 GB';
+            if (gb < 1) {
+                return (gb * 1024).toFixed(0) + ' MB';
+            }
+            return gb.toFixed(2) + ' GB';
+        },
+
+        /**
+         * Format timestamp
+         */
+        formatTime(timestamp) {
+            if (!timestamp) return 'Unknown';
+            try {
+                const date = new Date(timestamp);
+                return date.toLocaleTimeString();
+            } catch (e) {
+                return 'Unknown';
+            }
+        }
+    };
+}