feat: add generate-dev-db-events skill for seeding PostgreSQL demo data with bilingual support

Author: Robert27

.agents/skills/generate-dev-db-events/SKILL.md

@@ -0,0 +1,91 @@
+---
+name: generate-dev-db-events
+description: >-
+  Seeds or refreshes Campus Life Events PostgreSQL demo data via Docker Compose
+  Postgres. Generates bilingual (DE/EN) events with realistic timestamps, about
+  three to four events per calendar week, using existing organizers. Use when
+  the user asks for dev/demo events, seed data, filling the local database,
+  refreshing outdated demo events, or bulk INSERTs for events in backend/docker-compose.
+---
+
+# Generate dev database events
+
+## Preconditions
+
+- Postgres container from `backend/docker-compose.yml` is running (`cle-postgres`).
+- Inserts target the **`events`** table; **`organizer_id`** must reference an existing `organizers.id`.
+
+## Connection (local Compose)
+
+From `backend/docker-compose.yml`:
+
+| Setting | Value |
+|--------|--------|
+| Host (from machine) | `localhost` |
+| Port | **5422** |
+| User | `cle` |
+| Password | `cle_password` |
+| Database | `cle_db` |
+| Container name | `cle-postgres` |
+
+Shell:
+
+```bash
+docker exec -i cle-postgres psql -U cle -d cle_db -v ON_ERROR_STOP=1
+```
+
+**Important:** use `docker exec **-i**` when piping SQL or a heredoc into `psql`. Without `-i`, stdin is ignored and nothing runs.
+
+Host `psql` (if installed):
+
+```bash
+psql "postgres://cle:cle_password@localhost:5422/cle_db"
+```
+
+## `events` row shape
+
+Required / typical columns:
+
+- `organizer_id` (BIGINT, FK to `organizers`)
+- `title_de`, `title_en` (NOT NULL)
+- `description_de`, `description_en` (optional)
+- `start_date_time`, `end_date_time` (**both NOT NULL**; `end_date_time` must be after start)
+- `event_url`, `location` (optional)
+- `publish_app`, `publish_newsletter`, `publish_in_ical`, `publish_web` (BOOLEAN; default demo pattern: all `TRUE`)
+
+Use `TIMESTAMPTZ` strings with explicit offset, e.g. `2026-05-14T17:00:00+02` for Europe/Berlin summer time.
+
+## Cadence
+
+- Aim for **3–4 events per week** over the requested date range (e.g. one semester window).
+- Spread weekdays (e.g. Tue, Wed, Thu, Sat) to avoid unrealistic stacking unless the user asks otherwise.
+- Rotate **`organizer_id`** across existing organizers (query `SELECT id, name FROM organizers ORDER BY id` first).
+
+## Workflow
+
+1. List organizers: `SELECT id, name FROM organizers ORDER BY id;`
+2. Optionally clear old demo rows in the target window: `DELETE FROM events WHERE ...` (check `audit_log` for `event_id` if constraints exist).
+3. Generate `INSERT INTO events (...) VALUES (...), (...);` in batches.
+4. Apply with `docker exec -i cle-postgres psql -U cle -d cle_db -v ON_ERROR_STOP=1 <<'SQL' ... SQL`
+5. Verify density:
+
+```sql
+SELECT date_trunc('week', start_date_time)::date AS week_start, COUNT(*) AS n
+FROM events
+WHERE start_date_time >= 'YYYY-MM-DD' AND start_date_time < 'YYYY-MM-DD'
+GROUP BY 1 ORDER BY 1;
+```
+
+## Generation pattern (recommended)
+
+Use a short script (e.g. Python) to emit SQL: cycle organizer ids and event templates, fix `end` after `start`, escape single quotes in text as `''`, and print one multi-row `INSERT`.
+
+## Content guidelines
+
+- Bilingual **German / English** titles and descriptions matching campus-life tone.
+- Varied categories: sports, culture, tech workshops, sustainability, music, debate, international office, etc.
+- Prefer **plausible** locations and optional `https://example.edu/...` URLs for demos.
+
+## Optional cleanup
+
+If the user wants only the new cohort in a window, delete superseded rows by id or by `start_date_time` range after confirming no important FKs (e.g. `audit_log.event_id`).