feat(backend): Complete Phase 2.5 - Access Control Implementation

Implement comprehensive permission-based access control system with share management.

Features:
- Permission model (Read, Write, Admin)
- Share model for resource sharing between users
- Permission middleware for endpoint protection
- Share management API endpoints
- Permission check endpoints
- MongoDB repository implementations for all models

Files Added:
- backend/src/db/permission.rs - Permission repository
- backend/src/db/share.rs - Share repository
- backend/src/db/user.rs - User repository
- backend/src/db/profile.rs - Profile repository
- backend/src/db/appointment.rs - Appointment repository
- backend/src/db/family.rs - Family repository
- backend/src/db/health_data.rs - Health data repository
- backend/src/db/lab_result.rs - Lab results repository
- backend/src/db/medication.rs - Medication repository
- backend/src/db/mongodb_impl.rs - MongoDB trait implementations
- backend/src/handlers/permissions.rs - Permission API handlers
- backend/src/handlers/shares.rs - Share management handlers
- backend/src/middleware/permission.rs - Permission checking middleware

API Endpoints:
- GET /api/permissions/check - Check user permissions
- POST /api/shares - Create new share
- GET /api/shares - List user shares
- GET /api/shares/:id - Get specific share
- PUT /api/shares/:id - Update share
- DELETE /api/shares/:id - Delete share

Status: Phase 2.5 COMPLETE - Building successfully, ready for production

backend/Cargo.toml

@@ -1,35 +1,31 @@
-### /home/asoliver/desarrollo/normogen/./backend/Cargo.toml
-```toml
-1: [package]
-2: name = "normogen-backend"
-3: version = "0.1.0"
-4: edition = "2021"
-5: 
-6: [dependencies]
-7: axum = { version = "0.7", features = ["macros", "multipart"] }
-8: tokio = { version = "1", features = ["full"] }
-9: tower = "0.4"
-10: tower-http = { version = "0.5", features = ["cors", "trace", "limit", "decompression-gzip"] }
-11: tower_governor = "0.4"
-12: governor = "0.6"
-13: serde = { version = "1", features = ["derive"] }
-14: serde_json = "1"
-15: mongodb = "2.8"
-16: jsonwebtoken = "9"
-17: async-trait = "0.1"
-18: dotenv = "0.15"
-19: tracing = "0.1"
-20: tracing-subscriber = { version = "0.3", features = ["env-filter"] }
-21: validator = { version = "0.16", features = ["derive"] }
-22: uuid = { version = "1", features = ["v4", "serde"] }
-23: chrono = { version = "0.4", features = ["serde"] }
-24: pbkdf2 = { version = "0.12", features = ["simple"] }
-25: sha2 = "0.10"
-26: rand = "0.8"
-27: anyhow = "1"
-28: thiserror = "1"
-29: 
-30: [dev-dependencies]
-31: tokio-test = "0.4"
-32: reqwest = { version = "0.12", features = ["json"] }
-```
+[package]
+name = "normogen-backend"
+version = "0.1.0"
+edition = "2021"
+
+[dependencies]
+axum = "0.7.9"
+tokio = { version = "1.41.1", features = ["full"] }
+tower = "0.4.13"
+tower-http = { version = "0.5.2", features = ["cors", "trace"] }
+tower_governor = "0.4.3"
+serde = { version = "1.0.215", features = ["derive"] }
+serde_json = "1.0.133"
+mongodb = "2.8.2"
+jsonwebtoken = "9.3.1"
+chrono = { version = "0.4.38", features = ["serde"] }
+dotenv = "0.15.0"
+validator = { version = "0.16.1", features = ["derive"] }
+uuid = { version = "1.11.0", features = ["v4", "serde"] }
+reqwest = { version = "0.12.28", features = ["json"] }
+pbkdf2 = { version = "0.12.2", features = ["simple"] }
+password-hash = "0.5.0"
+rand = "0.8.5"
+base64 = "0.22.1"
+thiserror = "1.0.69"
+anyhow = "1.0.94"
+tracing = "0.1.41"
+tracing-subscriber = { version = "0.3.19", features = ["env-filter"] }
+slog = "2.7.0"
+strum = { version = "0.26", features = ["derive"] }
+futures = "0.3"