feat: replace Redis with PostgreSQL for caching, rate limiting, SMS codes, and token blacklist

- Add 4 PG entities: VerificationCode, RateLimitEntry, TokenBlacklistEntry, CacheEntry
- Add 4 services: VerificationService, RateLimitService, TokenBlacklistService, CacheService
- Add CleanupBackgroundService for periodic expired data cleanup
- Add MigrationHelper for safe schema migration without data loss
- Update AuthController: real SMS code generation, rate limiting, logout endpoint with JWT blacklist
- Update JwtProvider: add JTI claim for token revocation
- Update Program.cs: register new services, JWT blacklist validation, DB migration
- Remove StackExchange.Redis NuGet package and all Redis config references
- Update start-dev.bat: 6→5 services, remove Redis startup
- Update docs: remove Redis references from all documentation
- Fix: logout button spacing on profile page
- Fix: .gitignore data/→/data/ to not ignore Infrastructure/Data/

backend/src/HealthManager.Application/Services/CacheService.cs

@@ -0,0 +1,54 @@
+using System.Text.Json;
+using HealthManager.Domain.Entities;
+using HealthManager.Infrastructure.Data;
+using Microsoft.EntityFrameworkCore;
+
+namespace HealthManager.Application.Services;
+
+public class CacheService(AppDbContext db)
+{
+    private static readonly JsonSerializerOptions JsonOptions = new() { PropertyNameCaseInsensitive = true };
+
+    public async Task<T?> GetAsync<T>(string key) where T : class
+    {
+        var entry = await db.CacheEntries
+            .FirstOrDefaultAsync(c => c.Key == key && c.ExpiresAt > DateTime.UtcNow);
+        if (entry == null) return default;
+        return JsonSerializer.Deserialize<T>(entry.Value.RootElement.GetRawText(), JsonOptions);
+    }
+
+    public async Task SetAsync<T>(string key, T value, TimeSpan ttl)
+    {
+        var json = JsonSerializer.SerializeToDocument(value);
+        var existing = await db.CacheEntries.FirstOrDefaultAsync(c => c.Key == key);
+        if (existing != null)
+        {
+            existing.Value = json;
+            existing.ExpiresAt = DateTime.UtcNow.Add(ttl);
+        }
+        else
+        {
+            db.CacheEntries.Add(new CacheEntry
+            {
+                Key = key,
+                Value = json,
+                ExpiresAt = DateTime.UtcNow.Add(ttl),
+            });
+        }
+        await db.SaveChangesAsync();
+    }
+
+    public async Task<T> GetOrSetAsync<T>(string key, Func<Task<T>> factory, TimeSpan ttl) where T : class
+    {
+        var cached = await GetAsync<T>(key);
+        if (cached != null) return cached;
+        var value = await factory();
+        await SetAsync(key, value, ttl);
+        return value;
+    }
+
+    public async Task RemoveAsync(string key)
+    {
+        await db.CacheEntries.Where(c => c.Key == key).ExecuteDeleteAsync();
+    }
+}