Fix circular import, primary-admin NULL trap, and add gateway quota reset

Restores a working import graph and closes two data-correctness bugs, plus
adds a reset for the AI gateway's rolling 24h spend.

Circular import: database/__init__ -> engagement -> content -> utils ->
database made the package unimportable. get_project_devlog moves out of
database/engagement.py into content.py, where enrich_items already lives.

Primary administrator: _can_hold_primary_admin read is_active with
bool(row.get("is_active")), so an admin row whose is_active column is SQL
NULL (any row predating the column) was treated as deactivated and skipped.
Every other site defaults an unknown is_active to active; this one now does
too.

Profile JSON: xp_next_level and xp_progress_pct were computed but only put on
the top-level context, never on profile_user, so they serialised as null even
though UserOut declares them and the API docs document them as embedded there.

Gateway quota reset: a cap previously lifted only with the passage of time.
quota.reset upserts a watermark row into gateway_quota_resets, scoped by the
same three nullable dimensions as a quota rule, and spent_24h sums from
max(24h cutoff, watermark). No ledger row is deleted, so the cost analytics on
/admin/ai-usage stay intact. Reaches every surface: POST
/admin/gateway/quota-resets, a per-rule Reset spend button, the Devii tool
gateway_quota_reset (confirm-gated), devplace gateway quota reset, and the API
docs. Admin's Reset all quotas now stamps a global gateway watermark too,
which is what a caller stuck on "AI gateway daily quota exceeded" needed.

Startup: _backfill_gamification swept every xp=0 user on every boot in every
worker and could never converge, since a user with no content earns no XP.
It now intersects pending users with _milestone_candidates(). db.tables is a
live reflection, so it is hoisted out of the loops that probed it per row.

Docker: the dependency layer now depends on pyproject.toml only, so a source
edit no longer reinstalls every dependency and re-downloads Chromium.
Adds start_interval so the healthcheck probes during the start period, and a
docker-reload target, since docker-up does not restart an unchanged container.

Adds events.md, the audit event catalogue that README, CLAUDE.md, the quiz
docs and the tooling all referenced but which never existed: 288 keys across
28 categories, including the families built from a variable at the call site.

Test fixes: both devlog helpers dated post 0 as the newest while the tests
assumed post 2 was; a profile login posted username= to a form that takes
email=; a devlog assertion matched six buttons under strict mode; and the
primary-admin tests seeded founders newer than the back-dated fixture admin,
so they only passed without the api tier.

Full suite: 2989 passed, 1 skipped.

devplacepy/database/schema.py

@@ -1761,6 +1761,29 @@ def backfill_api_keys() -> int:
     return updated
 
 
+MILESTONE_SOURCES = (
+    ("posts", "user_uid"),
+    ("comments", "user_uid"),
+    ("projects", "user_uid"),
+    ("gists", "user_uid"),
+    ("follows", "follower_uid"),
+    ("follows", "following_uid"),
+    ("user_activity", "user_uid"),
+)
+
+
+def _milestone_candidates() -> set:
+    tables = db.tables
+    candidates = set()
+    for table, column in MILESTONE_SOURCES:
+        if table not in tables:
+            continue
+        for row in db.query(f"SELECT DISTINCT {column} AS uid FROM {table}"):
+            if row["uid"]:
+                candidates.add(row["uid"])
+    return candidates
+
+
 def _backfill_gamification():
     if "users" not in db.tables:
         return
@@ -1824,7 +1847,12 @@ def _backfill_gamification():
         )
 
     _authors_cache.clear()
-    for user in pending:
+    candidates = _milestone_candidates()
+    checked = [user for user in pending if user["uid"] in candidates]
+    for user in checked:
         check_milestone_badges(user["uid"])
-    logger.info(f"Gamification backfill processed {len(pending)} users")
+    logger.info(
+        f"Gamification backfill processed {len(pending)} users, "
+        f"{len(checked)} with milestone-eligible activity"
+    )