feat(skills): add db-snapshot skill

.claude/skills/db-snapshot/SKILL.md

@@ -0,0 +1,49 @@
+---
+name: db-snapshot
+description: Take a snapshot of the current MongoDB dev database state on request, using backend/scripts/DB/snapshot_dump.py. Trigger when the user asks to snapshot/save/backup the DB, or before starting a new feature per CLAUDE.md ("Always take a DB snapshot before implementing a new feature").
+---
+
+# DB Snapshot
+
+Dumps `player_bios` + `player_stats` + `fetch_log` from the dev MongoDB to a local JSON file under `backend/scripts/snapshots/` (the script resolves its output dir relative to its own location, `scripts/DB/../snapshots`; gitignored via the blanket `backend/scripts/*` rule — developer-local only, preserves `_id` linkage via BSON Extended JSON).
+
+## Steps
+
+### 1. Confirm the stack is up
+
+Mongo must be reachable on `localhost:27017`:
+
+```bash
+docker compose ps --format "{{.Service}} {{.State}}"
+```
+
+If `mongodb` isn't `running`, tell the user to `docker compose up -d mongodb` (or the full stack) before proceeding — do not start it yourself without asking.
+
+### 2. Determine the snapshot filename
+
+- If the user gave a name, use it (append `.json` if missing).
+- Otherwise, propose one based on context: current branch/feature name or a dated name (e.g. `dev-fantasy-platform-sport5.json`, `pre-rag-chat.json`), and confirm with the user before running — don't silently overwrite an existing snapshot with the same name.
+
+### 3. Run the dump
+
+From `backend/`, using the project's venv per CLAUDE.md:
+
+```bash
+.venv\Scripts\python scripts/DB/snapshot_dump.py <name>.json
+```
+
+Omitting `<name>.json` writes to the script's default (`cl-2025-2026.json`) — always pass an explicit name unless the user wants the default.
+
+### 4. Report the result
+
+Show the per-collection doc counts printed by the script and the output path (`backend/scripts/snapshots/<name>.json`). Remind the user this file is gitignored (local-only) — it is not committed or pushed.
+
+## Restoring (reference only)
+
+This skill only takes snapshots. To restore one later:
+
+```bash
+.venv\Scripts\python scripts/DB/snapshot_load.py <name>.json
+```
+
+Restoring **replaces** `player_bios`, `player_stats`, and `fetch_log` entirely — confirm with the user before running it, since it's destructive to current DB state.

README.md

@@ -178,6 +178,8 @@ Tests use `mongomock` — no running MongoDB required.
 
 ```bash
 # From backend/ with the stack up
-python scripts/DB/snapshot_dump.py   # → backend/snapshots/cl-2025-2026.json
+python scripts/DB/snapshot_dump.py   # → backend/scripts/snapshots/cl-2025-2026.json
 python scripts/DB/snapshot_load.py   # restore
 ```
+
+Claude Code users: the `db-snapshot` skill (`.claude/skills/db-snapshot/SKILL.md`) wraps these scripts for on-demand snapshots.