feat(timetable): catalog links, scoped overrides, tags, exam schedule and share assets

Iteration 3 of the timetable (README §8):

- Entries link to the course catalog on import (blank fields filled, the
  student's values win) and carry role (已选/旁听), category (course/exam/
  other) and a free tag; POST catalog/<id>/add/ adds a catalog course as 旁听.
- Per-week overrides (TimetableEntryOverride) back PATCH entries/<id>/ with
  scope all/single/following and a canceled flag; imported entries keep the
  student's edits across re-imports; GET entries/<id>/ and DELETE overrides.
- Settings expose the registered sources, the student's tags and hidden_tags;
  a new exam source matches the term's CourseExam rows (import_exam_schedule)
  to the student's courses; terms gain exam_week_start / teaching_weeks and
  the seed calendars cover the exam weeks.
- GET share/assets/ serves the mini-program code (wxacode, cached) and the
  official-account QR code for the poster.
- Spectacular enum names pinned for the new choice sets.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_012t4BD5H1P5nn2zF7oU6q9e

Author: tangmc0210

api/AGENTS.md

@@ -44,7 +44,7 @@ then be registered with `include()` in `api/urls.py`.
 | `org/` | Organization subscription listing and subscription status updates. | `/api/v2/org/` |
 | `generic/` | Cross-feature mini-program data, currently the homepage carousel. | `/api/v2/generic/` |
 | `pku_account/` | PKU (IAAA) account binding: portal login with one-time credentials, binding status, consents, unbinding. Contract in `timetable/README.md` §3. | `/api/v2/pku/` |
-| `timetable/` | Personal timetable: terms, week view, stored entries, portal/text import, settings, ICS link, subscribe-message quota, course-catalog search. Contract in `timetable/README.md` §4 and §6. | `/api/v2/timetable/` |
+| `timetable/` | Personal timetable: terms, week view, agenda, stored entries with per-week overrides (scoped edits) and catalog links, catalog search and quick add (旁听), portal/text import, settings (source toggles, hidden tags), ICS link, subscribe-message quota, exam schedule source, poster share assets. Contract in `timetable/README.md` §4, §6 and §8. | `/api/v2/timetable/` |
 | `academic_record/` | Consent-gated grade records fetched through the PKU binding: stored grades, live sync, deletion. Contract in `timetable/README.md` §6.2. | `/api/v2/grades/` |
 
 Many modules use DRF `DefaultRouter`; routes generated from ViewSets and

api/activity/serializers.py

@@ -7,6 +7,10 @@
 from app.models import Activity, Participation
 from app.utils import get_person_or_org
 
+# Named in SPECTACULAR_SETTINGS['ENUM_NAME_OVERRIDES'] so the schema keeps a
+# stable component name for the activity category enum.
+ACTIVITY_CATEGORY_CHOICES = Activity.ActivityCategory.choices
+
 
 class ActivitySummarySerializer(serializers.ModelSerializer):
     """Serializer for activity summary display."""

api/config.py

@@ -1,8 +1,9 @@
 """
 Configuration helpers for API layer.
 
-Covers the mini program (wx) login flow and the subscribe-message templates
-used by class reminders (``timetable/README.md`` §6.1).
+Covers the mini program (wx) login flow, the subscribe-message templates
+used by class reminders (``timetable/README.md`` §6.1) and the share
+assets of the timetable poster (§8.5).
 """
 from boot.config import ROOT_CONFIG
 from utils.config import Config, LazySetting
@@ -12,7 +13,10 @@
     "CONFIG",
     "DEFAULT_SUBSCRIBE_FIELDS",
     "DEFAULT_SUBSCRIBE_PAGE",
+    "DEFAULT_SHARE_PAGE",
+    "DEFAULT_SHARE_SLOGAN",
     "get_subscribe_template",
+    "get_share_config",
 ]
 
 # Semantic field -> WeChat template key, used when a template omits "fields".
@@ -23,6 +27,8 @@
     "note": "thing4",
 }
 DEFAULT_SUBSCRIBE_PAGE = "pages/timetable/index"
+DEFAULT_SHARE_PAGE = "pages/timetable/index"
+DEFAULT_SHARE_SLOGAN = "元培智慧书院 · YPPF"
 
 class WXMiniappConfig(Config):
     """
@@ -47,11 +53,34 @@ class WXMiniappConfig(Config):
     # Subscribe-message templates: {key: {"id", "fields", "page"}}. An empty
     # "id" disables that template (see get_subscribe_template).
     subscribe_templates = LazySetting("subscribe_templates", default={}, type=dict)
+    # Share assets of the timetable poster (timetable/README.md §8.5): the
+    # page the mini-program code opens, the code's env_version, the
+    # official-account QR code (absolute URL or a path under MEDIA_URL;
+    # empty → none) and the poster slogan.
+    share_miniapp_page = LazySetting(
+        "share/miniapp_page", default=DEFAULT_SHARE_PAGE, type=str)
+    share_env_version = LazySetting("share/env_version", default="release", type=str)
+    share_official_qrcode_url = LazySetting(
+        "share/official_qrcode_url", default="", type=str)
+    share_slogan = LazySetting("share/slogan", default=DEFAULT_SHARE_SLOGAN, type=str)
 
 
 CONFIG = WXMiniappConfig(ROOT_CONFIG, "wx_miniapp")
 
 
+def get_share_config() -> dict:
+    """
+    The ``wx_miniapp.share`` block with defaults filled in:
+    ``{"miniapp_page", "env_version", "official_qrcode_url", "slogan"}``.
+    """
+    return {
+        "miniapp_page": str(CONFIG.share_miniapp_page or DEFAULT_SHARE_PAGE).strip(),
+        "env_version": str(CONFIG.share_env_version or "release").strip(),
+        "official_qrcode_url": str(CONFIG.share_official_qrcode_url or "").strip(),
+        "slogan": str(CONFIG.share_slogan or DEFAULT_SHARE_SLOGAN).strip(),
+    }
+
+
 def get_subscribe_template(key: str) -> dict | None:
     """
     The subscribe-message template ``key`` of ``wx_miniapp.subscribe_templates``