Add Phase 1 critical endpoints: Config & Save/Load system

- Added ConfigController with 4 endpoints:
  - getGameConfig: Server config, feature flags, URLs
  - getServerTime: UTC timestamps
  - getFeatureFlags: Feature toggles
  - getServerStatus: Health check

- Added save/load system to ProgressionController:
  - POST /save/{synergyId}: Save JSON blob
  - GET /save/{synergyId}/load: Load JSON blob
  - Version tracking and timestamps

- Added PlayerSave entity to database:
  - Stores arbitrary JSON game state
  - Version tracking (increments on save)
  - LastModified timestamps

- Updated appsettings.json:
  - ServerSettings section (version, URLs, MOTD)
  - FeatureFlags section (7 feature toggles)

- Created migration: AddPlayerSavesAndConfig
- Updated ApiModels with new DTOs
- All endpoints tested and working

Phase 1 objectives complete:
✅ Synergy ID generation (already existed)
✅ Configuration endpoints (new)
✅ Save/load system (new)

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

RR3CommunityServer/Data/RR3DbContext.cs

@@ -24,6 +24,7 @@ public class RR3DbContext : DbContext
     public DbSet<GameAsset> GameAssets { get; set; }
     public DbSet<ModPack> ModPacks { get; set; }
     public DbSet<UserSettings> UserSettings { get; set; }
+    public DbSet<PlayerSave> PlayerSaves { get; set; }
 
     protected override void OnModelCreating(ModelBuilder modelBuilder)
     {
@@ -407,6 +408,16 @@ public class GameAsset
     public string? CustomAuthor { get; set; }
 }
 
+public class PlayerSave
+{
+    public int Id { get; set; }
+    public string SynergyId { get; set; } = string.Empty;
+    public string SaveDataJson { get; set; } = "{}";
+    public long Version { get; set; } = 1;
+    public DateTime LastModified { get; set; } = DateTime.UtcNow;
+    public DateTime CreatedAt { get; set; } = DateTime.UtcNow;
+}
+
 // Mod Pack entity - bundles of custom content
 public class ModPack
 {