Add conference series pages

docs/personal-data-yaml.md

@@ -283,6 +283,7 @@ Legacy fields:
 
 Common optional fields:
 
+- Series: `series`, a key from `conference_series.yaml`.
 - Trip/location: `trip`, `country`, `venue`, `address`, `latitude`, `longitude`.
 - Attendance: `going`, `registered`, `speaking`, `online`, `accommodation_booked`, `transport_booked`.
 - Partial attendance: `attend_start`, `attend_end`. These may be dates or timezone-aware datetimes and are used on trip pages instead of official dates.
@@ -294,6 +295,7 @@ Exact example:
 
 ```yaml
 - name: FOSDEM
+  series: fosdem
   topic: FOSDEM
   location: Brussels
   country: be
@@ -319,6 +321,7 @@ Tentative example:
 
 ```yaml
 - name: FOSDEM
+  series: fosdem
   topic: FOSDEM
   location: Brussels
   country: be
@@ -335,6 +338,7 @@ Approximate examples:
 
 ```yaml
 - name: Wikimedia Hackathon 2027
+  series: wikimedia-hackathon
   topic: Wikimedia
   location: Albania
   country: al
@@ -346,6 +350,7 @@ Approximate examples:
   hackathon: true
 
 - name: PyCascades 2027
+  series: pycascades
   topic: Python
   location: TBC
   dates:
@@ -355,6 +360,46 @@ Approximate examples:
     latest: 2027-03-31
 ```
 
+## `conference_series.yaml`
+
+Top-level shape: mapping from stable series ID to series metadata.
+
+Used by: conference list pages, conference series index/detail pages, and validation of `conferences.yaml` `series` references.
+
+Required fields for each series:
+
+- `name`: display name for the series.
+
+Common optional fields:
+
+- `topic`: default topic/category.
+- `cadence`: for example `annual` or `recurring`.
+- `usual_location`: common city/place when the event usually stays in one place.
+- `country`: common lowercase country code when stable.
+- `url`: series homepage.
+- `notes`: free-text generation or scheduling notes.
+
+Example:
+
+```yaml
+fosdem:
+  name: FOSDEM
+  topic: FOSDEM
+  cadence: annual
+  usual_location: Brussels
+  country: be
+  url: https://fosdem.org/
+  notes: Usually the weekend where Sunday is the first Sunday in February.
+
+geomob-london:
+  name: Geomob London
+  topic: Maps
+  cadence: recurring
+  usual_location: London
+  country: gb
+  url: https://thegeomob.com/
+```
+
 ## `entities.yaml`
 
 Top-level shape: list of people/entities.