feat(charts): medication chart matches other charts (7d trend + indicator + target-range)

Marc: "Bei Medikamenten zum Beispiel wird jetzt nicht 7-Tage-Schnitt,
Trend und Zielbereiche angezeigt. Das möchte ich natürlich für alle
Charts."

The medication-compliance chart shipped in v1.4.15 A4 (replacing the
static placeholder) was missing the trend chip + target-range
visualization the BP/weight/mood charts already paint. Bringing it to
parity:

- 7-day trend chip in the header: signed delta in percentage points
  with a metric-aware sentiment colour (rising compliance → green,
  falling → orange) and an arrow icon. Mirrors the bg-muted/40 chip
  pattern HealthChart uses for its weekly/monthly bucket label.
- New `computeMedicationTrend7d()` helper computes the delta as the
  mean of the most-recent 7 daily rates minus the mean of the prior 7
  (capped at a 14-day window). Mean-difference rather than slope so a
  single outlier day doesn't wag the indicator.
- Target-range visualization: added a 100 % goal ReferenceLine (green,
  solid-ish) ALONGSIDE the existing 80 % minimum-acceptable threshold
  (yellow, paler dash). Two lines together visualise the target range
  the way HealthChart's targetZone band does for BP/weight tiles.

Tests:
- 6 new unit tests pin computeMedicationTrend7d() including direction,
  delta, the 14-day cap, short windows, stable noise rejection.
- The existing chart-render snapshot is extended with an explicit
  assertion that the trend chip is suppressed in the empty state
  (so the empty-state header doesn't paint a misleading "0 pp"
  indicator).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

.env.example

@@ -82,6 +82,13 @@ API_TOKEN_HMAC_KEY="REPLACE-WITH-OUTPUT-OF-openssl-rand-hex-32"
 # Users bring their own API keys via Settings. No server-side key needed by
 # default. The admin can configure a fallback key in the Admin Panel.
 
+# Maximum number of comprehensive-insight generations a single user can
+# trigger per hour (POST /api/insights/generate). Default 10. The 24h
+# DB cache short-circuits this for read traffic; only force=true and
+# expired-cache regenerations consume tokens. Lower this when running
+# on a tight LLM budget.
+# INSIGHTS_RATE_LIMIT_PER_HOUR="10"
+
 
 # -----------------------------------------------------------------------------
 # Structured Logging — Wide Events (optional, sensible defaults)