Fix R8: Use builtins.fetchGit for submodule workspaces

- Added chainfireSrc, flaredbSrc, iamSrc with submodules=true
- Updated chainfire-server, flaredb-server, iam-server to use fetched sources
- Resolves T026.S1 blocker (nix build failures on submodule paths)

Implements fix suggested by Foreman 000313 and PeerA 000314

flake.nix

@@ -31,6 +31,23 @@
           inherit system overlays;
         };
 
+        # Fetch submodule sources with their .git directories included
+        # This is necessary because chainfire, flaredb, and iam are git submodules
+        chainfireSrc = builtins.fetchGit {
+          url = ./chainfire;
+          submodules = true;
+        };
+
+        flaredbSrc = builtins.fetchGit {
+          url = ./flaredb;
+          submodules = true;
+        };
+
+        iamSrc = builtins.fetchGit {
+          url = ./iam;
+          submodules = true;
+        };
+
         # Rust toolchain configuration
         # Using stable channel with rust-src (for rust-analyzer) and rust-analyzer
         rustToolchain = pkgs.rust-bin.stable.latest.default.override {
@@ -169,7 +186,7 @@
           # --------------------------------------------------------------------
           chainfire-server = buildRustWorkspace {
             name = "chainfire-server";
-            workspaceDir = ./chainfire;
+            workspaceDir = chainfireSrc;
             mainCrate = "chainfire-server";
             description = "Distributed key-value store with Raft consensus and gossip protocol";
           };
@@ -179,7 +196,7 @@
           # --------------------------------------------------------------------
           flaredb-server = buildRustWorkspace {
             name = "flaredb-server";
-            workspaceDir = ./flaredb;
+            workspaceDir = flaredbSrc;
             mainCrate = "flaredb-server";
             description = "Distributed time-series database with Raft consensus for metrics and events";
           };
@@ -189,7 +206,7 @@
           # --------------------------------------------------------------------
           iam-server = buildRustWorkspace {
             name = "iam-server";
-            workspaceDir = ./iam;
+            workspaceDir = iamSrc;
             mainCrate = "iam-server";
             description = "Identity and access management service with RBAC and multi-tenant support";
           };