Part 2 of #3485. WebDAV server (PROPFIND/GET/PUT/DELETE/MKCOL/MOVE/OPTIONS) handled in the custom server layer (standalone-server-ws.mjs) since the App Router cannot export WebDAV methods. Basic-Auth (constant-time), path-traversal hardened, password decrypt ported from encryption.ts (parity-tested), DATA_DIR resolution parity-tested against dataPaths.ts. End-to-end Obsidian-over-Tailscale validation is a live VPS step (Rule #18).
Integrated into release/v3.8.8. Applied review fixes: moved the SELECT 1 into a pingDb() db helper (no raw SQL in route, Hard Rule #5) + the 503 catch no longer leaks err.message (Hard Rule #12). Thanks @herjarsa!