fix: config key mismatch and safe Guid parsing in backend controllers

Backend/Backend/Controllers/AuthController.cs

@@ -73,7 +73,7 @@ public async Task<IActionResult> GitHubLogin([FromBody] string code)
             { "client_id", _config["GitHub:ClientId"]! },
             { "client_secret", _config["GitHub:ClientSecret"]! },
             { "code", code },
-            { "redirect_uri", _config["GitHub:RedirectUri"] ?? "" }
+            { "redirect_uri", _config["GitHub:CallbackUrl"] ?? "" }
         };
 
         using var request = new HttpRequestMessage(HttpMethod.Post, "https://github.com/login/oauth/access_token")

Backend/Backend/Controllers/IssuesController.cs

@@ -38,7 +38,8 @@ public async Task<IActionResult> ClaimQuest(long id)
         var userIdClaim = User.FindFirst(ClaimTypes.NameIdentifier)?.Value;
         if (string.IsNullOrEmpty(userIdClaim)) return Unauthorized("User ID missing from token.");
 
-        var userId = Guid.Parse(userIdClaim);
+        if (!Guid.TryParse(userIdClaim, out var userId))
+            return Unauthorized("Invalid user ID in token.");
 
         // Verify the issue exists in our database and is still active
         var issue = await _context.Issues.FirstOrDefaultAsync(i => i.GitHubIssueId == id);
@@ -76,9 +77,10 @@ public async Task<IActionResult> ClaimQuest(long id)
     public async Task<IActionResult> GetMyQuests()
     {
         var userIdClaim = User.FindFirst(ClaimTypes.NameIdentifier)?.Value;
-        if (userIdClaim == null) return Unauthorized();
+        if (userIdClaim == null) return Unauthorized("User ID missing from token.");
 
-        var userId = Guid.Parse(userIdClaim);
+        if (!Guid.TryParse(userIdClaim, out var userId))
+            return Unauthorized("Invalid user ID in token.");
         var quests = await _context.Quests
             .Where(q => q.UserId == userId && q.Status == "In Progress")
             .ToListAsync();
@@ -89,8 +91,9 @@ public async Task<IActionResult> GetMyQuests()
     public async Task<IActionResult> SubmitQuest(long id)
     {
         var userIdClaim = User.FindFirst(ClaimTypes.NameIdentifier)?.Value;
-        if (userIdClaim == null) return Unauthorized();
-        var userId = Guid.Parse(userIdClaim);
+        if (userIdClaim == null) return Unauthorized("User ID missing from token.");
+        if (!Guid.TryParse(userIdClaim, out var userId))
+            return Unauthorized("Invalid user ID in token.");
 
         var quest = await _context.Quests
             .FirstOrDefaultAsync(q => q.UserId == userId && q.GitHubIssueId == id && q.Status == "In Progress");

Backend/Backend/Services/GitHubService.cs

@@ -28,7 +28,7 @@ public GitHubService(HttpClient httpClient, IConfiguration config)
             client_id = section["ClientId"],
             client_secret = section["ClientSecret"],
             code = code,
-            redirect_uri = section["RedirectUri"]
+            redirect_uri = section["CallbackUrl"]
         };
 
         using var request = new HttpRequestMessage(HttpMethod.Post, "https://github.com/login/oauth/access_token")