Fix DHCP client unable to get IP and config not persisting

- Fixed verifyAssignment being too strict for new clients
- Fixed parseRequestedIP string conversion bug
- Fixed response sent to 0.0.0.0 instead of broadcast address
- Added SO_BROADCAST support for UDP socket
- Fixed session persistence after page refresh (localStorage)
- Added in-memory session store for auth middleware
- Added config reloader so DHCP server picks up web UI changes dynamically

.gitignore

@@ -0,0 +1,38 @@
+# Binaries
+*.exe
+*.exe~
+*.dll
+*.so
+*.dylib
+main
+dhcp-dns-manager
+
+# Test binary
+*.test
+
+# Output of the go coverage tool
+*.out
+
+# Dependency directories
+vendor/
+
+# Go workspace file
+go.work
+
+# Database
+*.db
+*.db-journal
+data/
+
+# IDE
+.idea/
+.vscode/
+*.swp
+*.swo
+
+# Logs
+*.log
+
+# OS
+.DS_Store
+Thumbs.db