Remove unused nuzlocke rules, reorganize into core and playstyle

Remove firstEncounterOnly, permadeath, nicknameRequired, and
postGameCompletion from the rules system — they are either implicit
(it's a nuzlocke tracker) or not enforced. Move levelCaps to core
(it's displayed in the sticky bar). Create a new "playstyle" category
for hardcoreMode and setModeOnly — informational rules useful for
stats but not enforced by the tracker. Remove the completion category
entirely. Add sub-task beans for the rules overhaul epic.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

backend/src/app/seeds/inject_test_data.py

@@ -142,14 +142,11 @@ RUN_DEFS = [
 
 # Default rules (matches frontend DEFAULT_RULES)
 DEFAULT_RULES = {
-    "firstEncounterOnly": True,
-    "permadeath": True,
-    "nicknameRequired": True,
     "duplicatesClause": True,
     "shinyClause": True,
     "pinwheelClause": True,
-    "hardcoreMode": False,
     "levelCaps": False,
+    "hardcoreMode": False,
     "setModeOnly": False,
 }