feat: WireGuard endpoint override + fix Docker network label issue

Endpoint override:
- Add PUT /api/wireguard/endpoint to set endpoint_override in identity
  config; GET returns detected, override, and effective endpoints
- _effective_endpoint() helper applies override in peer config generation
  (wireguard.py and peer_dashboard.py); detected IP still shown in UI
- Add Endpoint Override input in WireGuard page — solves the common case
  where auto-detected IP is a gateway/VPS but peers connect via LAN IP

Docker cell-network fix:
- Declare cell-network external in docker-compose.yml; Docker Compose v5
  enforces label ownership and rejects networks created by older versions
- Makefile start/update pre-create cell-network idempotently
- reinstall/uninstall(full) explicitly delete and recreate the network
- Fix uninstall loop path: data/api/services/ (not data/services/)

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

Makefile

@@ -180,7 +180,7 @@ uninstall:
 	case "$$ans" in \
 	  y|Y) \
 	    echo "Stopping containers and removing images..."; \
-	    for f in data/services/*/docker-compose.yml; do [ -f "$$f" ] && PUID=$$(id -u) PGID=$$(id -g) docker compose -f "$$f" down 2>/dev/null || true; done; \
+	    for f in data/api/services/*/docker-compose.yml; do [ -f "$$f" ] && PUID=$$(id -u) PGID=$$(id -g) docker compose -f "$$f" down 2>/dev/null || true; done; \
 	    PUID=$$(id -u) PGID=$$(id -g) $(DCF) --profile core down --rmi all 2>/dev/null || true; \
 	    docker network rm cell-network 2>/dev/null || true; \
 	    echo "Deleting config/ and data/..."; \
@@ -189,7 +189,7 @@ uninstall:
 	    ;; \
 	  n|N|"") \
 	    echo "Stopping and removing containers (keeping images and data)..."; \
-	    for f in data/services/*/docker-compose.yml; do [ -f "$$f" ] && PUID=$$(id -u) PGID=$$(id -g) docker compose -f "$$f" down 2>/dev/null || true; done; \
+	    for f in data/api/services/*/docker-compose.yml; do [ -f "$$f" ] && PUID=$$(id -u) PGID=$$(id -g) docker compose -f "$$f" down 2>/dev/null || true; done; \
 	    PUID=$$(id -u) PGID=$$(id -g) $(DCF) --profile core down 2>/dev/null || true; \
 	    echo "Done. Images, config/ and data/ are untouched. Run 'make start' to bring it back up."; \
 	    ;; \