fix: Docker build now compiles submodules correctly

- Remove .gitmodules from .dockerignore so the build loop can discover
  which directories to compile
- Add git to Dockerfile apt installs (needed for git config --file parsing)
- Gate git submodule update --init on .git presence, not .gitmodules;
  the compile loop still runs in Docker since .gitmodules is now present
- hashcat skipped in Docker build loop since system hashcat is in PATH

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Makefile

@@ -5,8 +5,8 @@ hashcat-utils: submodules
 	$(MAKE) -C hashcat-utils
 
 submodules:
-	@# Initialize submodules when present
-	@if [ -f .gitmodules ] && command -v git >/dev/null 2>&1; then \
+	@# Initialize submodules only when inside a git repo (not in Docker/CI copies)
+	@if [ -d .git ] && [ -f .gitmodules ] && command -v git >/dev/null 2>&1; then \
 		git submodule update --init --recursive; \
 	fi; \
 	$(MAKE) submodules-pre; \