trucking: compute coupon discounted prices on the fly (true per A/B arm) + fix CTA URL bug

Two correctness fixes that gate enabling the coupon test:

1. On-the-fly pricing. The coupon block hardcoded '$79 $47' (only true at 40%
   off) — a false claim on the 20/30% arms. Now build_trucking_campaigns.py
   reads api/src/service-catalog.ts (same source checkout uses) and computes
   coupon_price_full / coupon_price_deal per recipient as full - round(full*pct/100),
   exactly matching the server. Service-fee-only; non-discountable services
   (boc3-filing passthrough) get NO price and fall back to percent-only copy.
   Quotes the service the email is ABOUT (mcs150 $79, reactivation $149), not the
   bundle the CTA happens to link to. service-catalog.ts now ships in the worker
   image; helper degrades to percent-only if it can't be read.

2. CTA URL bug (likely a big driver of the zero-click problem). Main campaign
   CTAs render '/order/slug&utm_source=...' (no '?') -> HTTP 404, verified live.
   Deficiency CTAs would double-'?' once a coupon added '?code='. lp_link now
   owns the query (?dot=...&code=...) so every template appends with a leading
   '&' and is valid in all 4 states (main/deficiency x coupon on/off), verified
   against live URLs returning 200.

Deficiency _deal_box now shows real was/now prices (percent-only for boc3).
Tests: 7/7 pass (adds URL-wellformed + price-matches-checkout cases).

scripts/create_deficiency_source_campaigns.py

@@ -78,12 +78,59 @@ def _price_box(headline, sub):
     )
 
 
+def _deal_box(headline, sub):
+    """Coupon-aware offer box.
+
+    When the daily same-day coupon is active (coupon_code attrib set), show the
+    deal. If the build step computed a real discounted price for this service
+    (coupon_priceable set — true for discountable services), show the exact
+    "was $X, now $Y" numbers, which are calculated on the fly to match what
+    checkout charges (service fee only) for the current A/B arm. If the service
+    isn't discountable (e.g. BOC-3, a $25 passthrough) the price attribs are
+    blank and we fall back to percent-only copy so we never print a false price.
+    With no coupon at all it shows the normal price box.
+    """
+    priced = (
+        f'<p style="font-size:18px;font-weight:700;color:#9a3412;margin:0 0 6px">{headline} '
+        'for <span style="text-decoration:line-through;color:#c2410c;font-weight:600">'
+        '{{ .Subscriber.Attribs.coupon_price_full }}</span> '
+        '<span style="color:#15803d">{{ .Subscriber.Attribs.coupon_price_deal }}</span>.</p>'
+    )
+    unpriced = (
+        f'<p style="font-size:18px;font-weight:700;color:#9a3412;margin:0 0 6px">{headline}</p>'
+    )
+    deal = (
+        '<div style="background:#fff7ed;border:2px solid #f97316;border-radius:10px;'
+        'padding:20px;margin:20px 0;text-align:center">'
+        '<p style="font-size:13px;font-weight:700;color:#9a3412;letter-spacing:.04em;'
+        'margin:0 0 6px">TODAY ONLY - {{ .Subscriber.Attribs.coupon_pct }}% OFF OUR SERVICE FEE</p>'
+        '{{ if .Subscriber.Attribs.coupon_priceable }}' + priced + '{{ else }}' + unpriced + '{{ end }}'
+        '<p style="font-size:14px;color:#9a3412;margin:0 0 4px">Use code '
+        '<strong style="font-size:16px;letter-spacing:.08em">{{ .Subscriber.Attribs.coupon_code }}</strong> '
+        '(already applied when you click below).</p>'
+        '<p style="font-size:12px;color:#b91c1c;font-weight:700;margin:0">'
+        'Expires {{ .Subscriber.Attribs.coupon_expires }}. Discount applies to our '
+        'service fee; government filing fees are billed at cost.</p></div>'
+    )
+    return (
+        '{{ if .Subscriber.Attribs.coupon_code }}'
+        + deal
+        + '{{ else }}'
+        + _price_box(headline, sub)
+        + '{{ end }}'
+    )
+
+
 def _cta(label):
     # Clicks land on the per-subscriber order page (resolved per row, incl.
-    # per-state overrides) via the lp_link attrib, with UTM tracking.
+    # per-state overrides) via the lp_link attrib. lp_link already carries the
+    # carrier's `?dot=` query (and the daily `?code=` when a coupon is active),
+    # so the template appends its own params with a leading `&` — correct whether
+    # or not the coupon is on. (Previously this used `?dot=`, which double-`?`d
+    # the URL once the coupon added its own query.)
     return (
         '<div style="text-align:center;margin:24px 0">'
-        '<a href="{{ .Subscriber.Attribs.lp_link }}?dot={{ .Subscriber.Attribs.dot_number }}'
+        '<a href="{{ .Subscriber.Attribs.lp_link }}'
         '&utm_source=listmonk&utm_medium=email&utm_campaign=deficiency@TrackLink" '
         'style="display:inline-block;padding:14px 36px;background:#f97316;color:#fff;'
         f'font-weight:700;border-radius:8px;text-decoration:none;font-size:16px">{label} &rarr;</a></div>'
@@ -124,7 +171,7 @@ def _body(headline, intro, bullets, price_headline, price_sub, cta_label):
         'computer. No Login.gov, no government portals, no hours on hold. We handle the paperwork so you can get '
         'back to trucking and making money.</p></div>'
     )
-    return (_HEADER + alert + _price_box(price_headline, price_sub) + reassure
+    return (_HEADER + alert + _deal_box(price_headline, price_sub) + reassure
             + _cta(cta_label) + _dot_check_cta() + _FOOTER)