refactor: consolidate formatting utilities and add testing infrastructure

- Replace 8 duplicate formatCurrency functions with shared utility
- Add comprehensive formatter utilities (currency, date, number, etc.)
- Set up Vitest for unit testing with 38 passing tests
- Set up Playwright for E2E testing
- Consolidate database connection to single source (src/utils/db.ts)
- Add auth middleware helpers to reduce code duplication
- Fix display bug: remove spurious minus sign in recent activity amounts
- Add path aliases for cleaner imports ($utils, $models)
- Add project documentation (CODEMAP.md, REFACTORING_PLAN.md)

Test coverage: 38 unit tests passing
Build: successful with no breaking changes

src/routes/api/fitness/exercises/+server.ts

@@ -0,0 +1,91 @@
+import { json } from '@sveltejs/kit';
+import type { RequestHandler } from './$types';
+import { dbConnect } from '$utils/db';
+import { Exercise } from '../../../../models/Exercise';
+
+// GET /api/fitness/exercises - Search and filter exercises
+export const GET: RequestHandler = async ({ url, locals }) => {
+  const session = await locals.auth();
+  if (!session || !session.user?.nickname) {
+    return json({ error: 'Unauthorized' }, { status: 401 });
+  }
+
+  try {
+    await dbConnect();
+    
+    // Query parameters
+    const search = url.searchParams.get('search') || '';
+    const bodyPart = url.searchParams.get('bodyPart') || '';
+    const equipment = url.searchParams.get('equipment') || '';
+    const target = url.searchParams.get('target') || '';
+    const difficulty = url.searchParams.get('difficulty') || '';
+    const limit = parseInt(url.searchParams.get('limit') || '50');
+    const offset = parseInt(url.searchParams.get('offset') || '0');
+
+    // Build query
+    let query: any = { isActive: true };
+    
+    // Text search
+    if (search) {
+      query.$text = { $search: search };
+    }
+    
+    // Filters
+    if (bodyPart) query.bodyPart = bodyPart.toLowerCase();
+    if (equipment) query.equipment = equipment.toLowerCase();
+    if (target) query.target = target.toLowerCase();
+    if (difficulty) query.difficulty = difficulty.toLowerCase();
+
+    // Execute query
+    let exerciseQuery = Exercise.find(query);
+    
+    // Sort by relevance if searching, otherwise alphabetically
+    if (search) {
+      exerciseQuery = exerciseQuery.sort({ score: { $meta: 'textScore' } });
+    } else {
+      exerciseQuery = exerciseQuery.sort({ name: 1 });
+    }
+    
+    const exercises = await exerciseQuery
+      .limit(limit)
+      .skip(offset)
+      .select('exerciseId name gifUrl bodyPart equipment target difficulty');
+    
+    const total = await Exercise.countDocuments(query);
+    
+    return json({ exercises, total, limit, offset });
+  } catch (error) {
+    console.error('Error fetching exercises:', error);
+    return json({ error: 'Failed to fetch exercises' }, { status: 500 });
+  }
+};
+
+// GET /api/fitness/exercises/filters - Get available filter options
+export const POST: RequestHandler = async ({ locals }) => {
+  const session = await locals.auth();
+  if (!session || !session.user?.nickname) {
+    return json({ error: 'Unauthorized' }, { status: 401 });
+  }
+
+  try {
+    await dbConnect();
+    
+    const [bodyParts, equipment, targets] = await Promise.all([
+      Exercise.distinct('bodyPart', { isActive: true }),
+      Exercise.distinct('equipment', { isActive: true }),
+      Exercise.distinct('target', { isActive: true })
+    ]);
+    
+    const difficulties = ['beginner', 'intermediate', 'advanced'];
+    
+    return json({
+      bodyParts: bodyParts.sort(),
+      equipment: equipment.sort(),
+      targets: targets.sort(),
+      difficulties
+    });
+  } catch (error) {
+    console.error('Error fetching filter options:', error);
+    return json({ error: 'Failed to fetch filter options' }, { status: 500 });
+  }
+};