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/Controllers/ProgressionController.cs

@@ -344,4 +344,107 @@ public class ProgressionController : ControllerBase
             totalExperience = user.Experience
         });
     }
+
+    /// <summary>
+    /// Save player game state as JSON blob
+    /// </summary>
+    [HttpPost("save/{synergyId}")]
+    public async Task<IActionResult> SavePlayerData(string synergyId, [FromBody] SaveDataRequest request)
+    {
+        _logger.LogInformation("Saving data for {SynergyId} ({Bytes} bytes)",
+            synergyId, request.SaveData?.Length ?? 0);
+
+        if (string.IsNullOrEmpty(request.SaveData))
+        {
+            return BadRequest(new { error = "Save data is empty" });
+        }
+
+        // Find or create save record
+        var save = await _context.PlayerSaves
+            .FirstOrDefaultAsync(s => s.SynergyId == synergyId);
+
+        if (save == null)
+        {
+            save = new PlayerSave
+            {
+                SynergyId = synergyId,
+                SaveDataJson = request.SaveData,
+                Version = 1,
+                CreatedAt = DateTime.UtcNow,
+                LastModified = DateTime.UtcNow
+            };
+            _context.PlayerSaves.Add(save);
+        }
+        else
+        {
+            save.SaveDataJson = request.SaveData;
+            save.Version++;
+            save.LastModified = DateTime.UtcNow;
+        }
+
+        await _context.SaveChangesAsync();
+
+        var response = new SynergyResponse<SaveDataResponse>
+        {
+            resultCode = 0,
+            message = "Save successful",
+            data = new SaveDataResponse
+            {
+                Success = true,
+                Version = save.Version,
+                LastModified = new DateTimeOffset(save.LastModified).ToUnixTimeSeconds(),
+                SaveData = string.Empty // Don't echo back the full data
+            }
+        };
+
+        return Ok(response);
+    }
+
+    /// <summary>
+    /// Load player game state JSON blob
+    /// </summary>
+    [HttpGet("save/{synergyId}/load")]
+    public async Task<IActionResult> LoadPlayerData(string synergyId)
+    {
+        _logger.LogInformation("Loading save data for {SynergyId}", synergyId);
+
+        var save = await _context.PlayerSaves
+            .FirstOrDefaultAsync(s => s.SynergyId == synergyId);
+
+        if (save == null)
+        {
+            // Return empty save for new players
+            var emptySave = new SaveDataResponse
+            {
+                SaveData = "{}",
+                Version = 0,
+                LastModified = DateTimeOffset.UtcNow.ToUnixTimeSeconds(),
+                Success = true
+            };
+
+            var emptyResponse = new SynergyResponse<SaveDataResponse>
+            {
+                resultCode = 0,
+                message = "No save found - new player",
+                data = emptySave
+            };
+
+            return Ok(emptyResponse);
+        }
+
+        var response = new SynergyResponse<SaveDataResponse>
+        {
+            resultCode = 0,
+            message = "Save loaded successfully",
+            data = new SaveDataResponse
+            {
+                SaveData = save.SaveDataJson,
+                Version = save.Version,
+                LastModified = new DateTimeOffset(save.LastModified).ToUnixTimeSeconds(),
+                Success = true
+            }
+        };
+
+        return Ok(response);
+    }
 }