Rewrite Python comments in Google developer documentation style (#12)

* Rewrite comments in Google developer documentation style

Rewrite the comments and docstrings across the backend core modules so they
read plainly. The previous prose was accurate but dense and figurative, which
made it slow to skim.

Applies the Google developer documentation style guide: short sentences, active
voice, present tense, American spelling, and no metaphors, idioms, or
rhetorical asides. Replaces em-dash chains with separate sentences.

backend/app/routers/analytics.py

@@ -1,10 +1,10 @@
 """Visit analytics: one endpoint the browser writes to, one the owner reads.
 
-The split matters. `/collect` is public and takes exactly one fact — which
-page was viewed — because anything a stranger can POST is a number a stranger
-can invent. Everything the dashboard actually relies on (turns, adventures,
-sign-ups, demo spend, errors) is recorded server-side by the code performing
-it, so those counts are as trustworthy as the app itself.
+The split matters. `/collect` is public and accepts one fact, which page was
+viewed, because anything a stranger can POST is a number a stranger can invent.
+Everything the dashboard relies on, meaning turns, adventures, sign-ups, demo
+spend, and errors, is recorded on the server by the code that performs it, so
+those counts are as trustworthy as the app itself.
 
 The two reading endpoints are owner-only and 404 for everyone else, the same
 way the AI Chat router does: a feature nobody else can use is better off not
@@ -27,7 +27,8 @@ def owner(
     db: Session = Depends(get_db),
     user: models.User = Depends(auth.get_current_user),
 ) -> models.User:
-    """Gate for the reading half. 404, not 403 — see the module docstring."""
+    """Gates the reading half. It returns 404 rather than 403. See the module
+    docstring."""
     if not auth.is_owner(user):
         raise HTTPException(404, "Not found")
     return user
@@ -39,10 +40,10 @@ Owner = Depends(owner)
 class Pageview(BaseModel):
     """What the SPA reports on a page load or a route change.
 
-    `first` marks a real page load rather than a client-side navigation: the
-    things that describe a *visit* rather than a *view* — where it came from,
-    on what kind of device, from which country — are recorded only then, so a
-    visitor who clicks around five pages is still one referral.
+    `first` marks a real page load rather than a client-side navigation. The
+    facts that describe a visit rather than a view, which are where it came from,
+    on what kind of device, and from which country, are recorded only on a page
+    load, so a visitor who clicks through five pages is still one referral.
     """
 
     path: str = Field("", max_length=300)
@@ -67,9 +68,9 @@ def collect(
         if auth.MULTI_USER
         else auth.local_user(db)
     )
-    # The operator's own clicking is not traffic. Only in multi-user mode —
-    # locally everyone is the owner, and excluding them would leave the
-    # dashboard permanently empty on the machine it is developed on.
+    # The operator's own clicks are not traffic. This applies only in
+    # multi-user mode. Locally every user is the owner, and excluding them would
+    # leave the dashboard empty on the machine the app is developed on.
     if auth.MULTI_USER and user is not None and auth.is_owner(user):
         return Response(status_code=204)
 
@@ -95,8 +96,10 @@ def summary(
     db: Session = Depends(get_db),
     _user: models.User = Owner,
 ) -> dict:
-    """The whole dashboard in one aggregate response — a few kilobytes however
-    much traffic sits behind it."""
+    """Returns the whole dashboard in one aggregate response.
+
+    The response is a few kilobytes however much traffic is behind it.
+    """
     return analytics.summary(db, days)
 
 
@@ -111,9 +114,9 @@ def access_log(
 ) -> dict:
     """A page of the access log, newest first.
 
-    Unlike /summary this returns rows about people, which is the whole point of
-    it — so it is behind the same owner gate, paged rather than dumped, and has
-    no counterpart the people it describes can reach.
+    Unlike `/summary`, this returns rows about people, which is what it is for.
+    It is therefore behind the same owner gate, it is paged rather than returned
+    in full, and the people it describes have no endpoint that reaches it.
     """
     page = accesslog.recent(
         db, limit=limit, before_id=before_id, kind=kind, query=q