Give climate/city/record pages full header parity + working °F/°C (#124)

The server-rendered SEO pages shared base.html.j2's nav but carried no JS, so
they lacked the °F/°C toggle and account/bell, and their temperatures were baked
as dual-unit strings that couldn't respond to a toggle.

- Load units.js + account.js + climate.js on base.html.j2, so every SEO page gets
  the same header as the interactive pages (nav + °F/°C toggle + account + bell).
- Emit each temperature as <span class="temp" data-temp-f> (default °F text, real
  for crawlers/no-JS); climate.js rewrites them to the active unit on load and on
  toggle. Tint classes stay pinned to absolute °F. Drops the inline "(NN°C)".
- Make account.js base-aware: derive the app base from import.meta.url so its
  api/v2 fetches and the alerts links resolve from deep /climate/{slug} URLs
  instead of 404ing. Equivalent on the depth-1 interactive pages.
- Default the unit from the browser locale for first-time visitors (no stored
  pref): en-US → °F, everyone else → °C. A stored choice always wins.

content.py

@@ -14,6 +14,7 @@ import polars as pl
 from fastapi import HTTPException, Request, Response
 from fastapi.responses import PlainTextResponse
 from jinja2 import Environment, FileSystemLoader, select_autoescape
+from markupsafe import Markup
 
 import cities
 import city_events
@@ -61,11 +62,22 @@ def _c(f: float) -> int:
     return round((f - 32) * 5 / 9)
 
 
-def _temp(f) -> str:
-    """A Fahrenheit value shown in both units: '72°F (22°C)'."""
+def _temp(f):
+    """A Fahrenheit temperature as a client-convertible span, e.g.
+    '<span class="temp" data-temp-f="72.3">72°F</span>'. Renders °F by default
+    (so crawlers and no-JS visitors see a real value); climate.js rewrites it to
+    the active unit on load and on toggle. Returns '—' for a missing value."""
     if f is None:
         return "—"
-    return f"{round(f)}°F ({_c(f)}°C)"
+    return Markup('<span class="temp" data-temp-f="{:.1f}">{}°F</span>').format(f, round(f))
+
+
+def _temp_bare(f):
+    """Like _temp() but with no unit letter ('72°'), for the range strip where the
+    axis already implies the unit. Still carries data-temp-f so it converts."""
+    if f is None:
+        return "—"
+    return Markup('<span class="temp" data-temp-f="{:.1f}" data-bare>{}°</span>').format(f, round(f))
 
 
 def _fmt(metric: str, v) -> str:
@@ -119,6 +131,8 @@ def _range_bar(low_f, high_f) -> dict | None:
 
 
 _env.globals["temp_class"] = temp_class
+_env.globals["temp"] = _temp
+_env.globals["temp_bare"] = _temp_bare
 
 
 def _month_doy(month_idx: int) -> int:
@@ -402,10 +416,10 @@ def _month_context(request, city, history, month_idx: int) -> dict:
     stats = []
     if tmax:
         stats.append(("Average high", _temp(tmax["mean"])))
-        stats.append(("Typical high range", f"{_temp(tmax['p10'])} to {_temp(tmax['p90'])}"))
+        stats.append(("Typical high range", _temp(tmax['p10']) + " to " + _temp(tmax['p90'])))
     if tmin:
         stats.append(("Average low", _temp(tmin["mean"])))
-        stats.append(("Typical low range", f"{_temp(tmin['p10'])} to {_temp(tmin['p90'])}"))
+        stats.append(("Typical low range", _temp(tmin['p10']) + " to " + _temp(tmin['p90'])))
     if precip:
         stats.append(("Average daily precipitation", f"{precip['mean']:.2f} in"))
     # Record high and low for every metric in this calendar month (mirrors the

templates/about.html.j2

@@ -23,7 +23,7 @@
      within <b>&plusmn;7 days of that day-of-year</b> — a 15-day seasonal window across all years. The
      observed value is placed on that distribution as an <a href="{{ base }}/glossary/percentile">empirical
      percentile</a>, then mapped to a grade from “Below Normal” through “High” to “Near Record”.</p>
-  <p>Everything is <b>relative to the location</b>: a 60&deg;F day can be “Above Normal” in one place and
+  <p>Everything is <b>relative to the location</b>: a {{ temp(60) }} day can be “Above Normal” in one place and
      “Below Normal” in another. Precipitation is graded only among days that actually rained, so “Heavy”
      means heavy for a rainy day <i>here</i>. See the <a href="{{ base }}/legend">grade guide</a> for the full scale.</p>
 

templates/base.html.j2

@@ -60,5 +60,10 @@
     <p class="muted">Thermograph grades weather by its percentile against ~45 years of local
        climate history. Climate data via Open-Meteo (ERA5 reanalysis).</p>
   </footer>
+  <!-- Header parity with the interactive pages: the °F/°C toggle, account + bell,
+       and the client-side temperature converter. All self-contained modules. -->
+  <script type="module" src="{{ base }}/units.js"></script>
+  <script type="module" src="{{ base }}/account.js"></script>
+  <script type="module" src="{{ base }}/climate.js"></script>
 </body>
 </html>

templates/city.html.j2

@@ -76,14 +76,14 @@
           {% if m.bar %}<span class="range-fill" style="left:{{ m.bar.left }}%;width:{{ m.bar.width }}%;--c1:var(--{{ m.bar.c1 }});--c2:var(--{{ m.bar.c2 }})"></span>{% endif %}
         </span>
         {% if m.range_lo_f is not none and m.range_hi_f is not none %}
-        <span class="range-vals">{{ m.range_lo_f | round | int }}°–{{ m.range_hi_f | round | int }}°</span>
+        <span class="range-vals">{{ temp_bare(m.range_lo_f) }}–{{ temp_bare(m.range_hi_f) }}</span>
         {% else %}<span class="range-vals">—</span>{% endif %}
       </div>
       {% endfor %}
     </div>
     <p class="range-note muted">Each bar spans the 10th-percentile daily low to the 90th-percentile daily
        high — the range most days fall within — coloured cold&nbsp;→&nbsp;hot on a shared
-       −10&nbsp;°F to 115&nbsp;°F scale, so the whole year's rhythm reads at a glance.</p>
+       {{ temp(-10) }} to {{ temp(115) }} scale, so the whole year's rhythm reads at a glance.</p>
   </section>
 
   <section class="city-travel">
@@ -97,10 +97,8 @@
   <section class="climate-records">
     <h2>Record extremes</h2>
     <ul>
-      {% if records.tmax %}<li><b>Hottest day on record:</b> {{ records.tmax.max | round | int }}°F
-        ({{ ((records.tmax.max - 32) * 5 / 9) | round | int }}°C) on {{ records.tmax.max_date }}</li>{% endif %}
-      {% if records.tmin %}<li><b>Coldest day on record:</b> {{ records.tmin.min | round | int }}°F
-        ({{ ((records.tmin.min - 32) * 5 / 9) | round | int }}°C) on {{ records.tmin.min_date }}</li>{% endif %}
+      {% if records.tmax %}<li><b>Hottest day on record:</b> {{ temp(records.tmax.max) }} on {{ records.tmax.max_date }}</li>{% endif %}
+      {% if records.tmin %}<li><b>Coldest day on record:</b> {{ temp(records.tmin.min) }} on {{ records.tmin.min_date }}</li>{% endif %}
     </ul>
     <p><a href="{{ base }}/climate/{{ city.slug }}/records">All {{ name }} weather records →</a></p>
   </section>

templates/records.html.j2

@@ -22,10 +22,8 @@
   <p class="lede">Record high and low temperatures for <b>{{ display }}</b> — by month, by season, and
      all-time — with the dates they occurred, across {{ year_range[0] }}–{{ year_range[1] }} of daily
      climate history.{% if all_time.tmax and all_time.tmin %} Its hottest day on record reached
-     {{ all_time.tmax.max | round | int }}°F ({{ ((all_time.tmax.max - 32) * 5 / 9) | round | int }}°C)
-     on {{ all_time.tmax.max_date }}; its coldest fell to
-     {{ all_time.tmin.min | round | int }}°F ({{ ((all_time.tmin.min - 32) * 5 / 9) | round | int }}°C)
-     on {{ all_time.tmin.min_date }}.{% endif %}</p>
+     {{ temp(all_time.tmax.max) }} on {{ all_time.tmax.max_date }}; its coldest fell to
+     {{ temp(all_time.tmin.min) }} on {{ all_time.tmin.min_date }}.{% endif %}</p>
 
   <section class="climate-records-section">
     <h2>Records by month</h2>

tests/test_content.py

@@ -171,3 +171,23 @@ def test_hub_glossary_about(client):
     assert client.get(f"{B}/glossary/percentile").status_code == 200
     assert client.get(f"{B}/glossary/not-a-term").status_code == 404
     assert client.get(f"{B}/about").status_code == 200
+
+
+def test_climate_pages_carry_convertible_temps(client):
+    # Every temperature is a client-convertible span (default °F text so crawlers
+    # and no-JS visitors still see a real value); the old inline "(NN°C)" dual form
+    # is gone (the toggle now supplies Celsius).
+    import re
+    for path in (f"{B}/climate/{SLUG}", f"{B}/climate/{SLUG}/july", f"{B}/climate/{SLUG}/records"):
+        b = client.get(path).text
+        assert 'class="temp" data-temp-f=' in b
+        assert "°F" in b
+        assert re.search(r"\d+°F \(-?\d+°C\)", b) is None   # no leftover dual-unit strings
+
+
+def test_seo_pages_load_unit_and_account_scripts(client):
+    # Header parity with the interactive pages: the °F/°C toggle, account/bell, and
+    # the temperature converter are all loaded.
+    b = client.get(f"{B}/climate/{SLUG}").text
+    for src in (f"{B}/units.js", f"{B}/account.js", f"{B}/climate.js"):
+        assert f'src="{src}"' in b