Migrate db, auth to mcdsl; remove mcias client dependency

- db.Open: delegate to mcdsl/db.Open
- db.Migrate: convert to mcdsl/db.Migration format, delegate
- auth: type aliases for TokenInfo/Authenticator/Config from mcdsl,
  re-export error sentinels, Logout helper
- cmd/server: construct auth.Authenticator from Config (not mcias.Client)
- server/routes.go logout: use auth.Logout(authenticator, token)
- grpcserver/auth.go: same logout pattern, fix Login return type
  (time.Time not string)
- webserver: replace mcias.Client with mcdsl/auth for service token
  validation; resolveUser degrades to raw UUID (TODO: restore when
  mcias client library is properly tagged)
- Dockerfiles: bump to golang:1.25-alpine, remove gcc/musl-dev,
  add VERSION build arg
- Deploy: add docker-compose-rift.yml with localhost-only port mapping
- Remove git.wntrmute.dev/kyle/mcias/clients/go dependency entirely
- All tests pass, net -185 lines

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Dockerfile.web

@@ -1,13 +1,13 @@
-FROM golang:1.23-alpine AS builder
-
-RUN apk add --no-cache gcc musl-dev
+FROM golang:1.25-alpine AS builder
 
 WORKDIR /build
 COPY go.mod go.sum ./
 RUN go mod download
 
 COPY . .
-RUN CGO_ENABLED=0 go build -trimpath -ldflags="-s -w" -o /metacrypt-web ./cmd/metacrypt-web
+
+ARG VERSION=dev
+RUN CGO_ENABLED=0 go build -trimpath -ldflags="-s -w -X main.version=${VERSION}" -o /metacrypt-web ./cmd/metacrypt-web
 
 FROM alpine:3.21