feat: Migrate Street and Task models from MongoDB to CouchDB

- Replace Street model with CouchDB-based implementation
- Replace Task model with CouchDB-based implementation
- Update routes to use new model interfaces
- Handle geospatial queries with CouchDB design documents
- Maintain adoption functionality and middleware
- Use denormalized document structure with embedded data
- Update test files to work with new models
- Ensure API compatibility while using CouchDB underneath

🤖 Generated with [AI Assistant]

Co-Authored-By: AI Assistant <noreply@ai-assistant.com>

backend/services/couchdbService.js

@@ -123,14 +123,31 @@ class CouchDBService {
         },
         indexes: {
           "streets-by-location": {
-            index: { fields: ["type", "location"] },
+            index: { 
+              fields: ["type", "location"],
+              partial_filter_selector: { "type": "street" }
+            },
             name: "streets-by-location",
             type: "json"
           },
           "streets-by-status": {
-            index: { fields: ["type", "status"] },
+            index: { 
+              fields: ["type", "status"],
+              partial_filter_selector: { "type": "street" }
+            },
             name: "streets-by-status",
             type: "json"
+          },
+          "streets-geo": {
+            index: {
+              fields: ["type", "location"],
+              partial_filter_selector: { 
+                "type": "street",
+                "location": { "$exists": true }
+              }
+            },
+            name: "streets-geo",
+            type: "json"
           }
         }
       },
@@ -729,15 +746,37 @@ class CouchDBService {
 
   // Street-specific operations
   async findStreetsByLocation(bounds) {
-    return this.find({
-      type: 'street',
-      status: 'available',
-      location: {
-        $geoWithin: {
-          $box: bounds
+    try {
+      // For CouchDB, we need to handle geospatial queries differently
+      // We'll use a bounding box approach with the geo index
+      const [sw, ne] = bounds;
+      
+      const query = {
+        selector: {
+          type: 'street',
+          status: 'available',
+          location: {
+            $exists: true
+          }
+        },
+        limit: 1000 // Reasonable limit for geographic queries
+      };
+
+      const streets = await this.find(query);
+      
+      // Filter by bounding box manually (since CouchDB doesn't support $geoWithin in Mango)
+      return streets.filter(street => {
+        if (!street.location || !street.location.coordinates) {
+          return false;
         }
-      }
-    });
+        
+        const [lng, lat] = street.location.coordinates;
+        return lng >= sw[0] && lng <= ne[0] && lat >= sw[1] && lat <= ne[1];
+      });
+    } catch (error) {
+      console.error("Error finding streets by location:", error.message);
+      throw error;
+    }
   }
 
   async adoptStreet(userId, streetId) {