feat(contribution): port join.vue to ContributionAmountField

Replace inline cadence radios, contribution input + presets, guidance
label, and billing summary with the shared ContributionAmountField
component. Removes duplicated state (guidanceLabel, firstCharge),
unused imports (CONTRIBUTION_PRESETS, getGuidanceLabel), and the
matching CSS rules. The parent retains the cadence ref because
formatContributionAmount (left-column tier list) reads it.

app/pages/join.vue

@@ -129,7 +129,7 @@
                   type="text"
                   placeholder="Your name"
                   required
-                />
+                >
               </div>
               <div class="form-group">
                 <label class="form-label" for="join-email">Email Address</label>
@@ -140,7 +140,7 @@
                   type="email"
                   placeholder="you@example.com"
                   required
-                />
+                >
               </div>
               <div class="form-group">
                 <label class="form-label">Circle</label>
@@ -152,7 +152,7 @@
                       type="radio"
                       name="circle"
                       value="community"
-                    />
+                    >
                     <label for="circle-community">
                       <span
                         class="circle-label-name"
@@ -169,7 +169,7 @@
                       type="radio"
                       name="circle"
                       value="founder"
-                    />
+                    >
                     <label for="circle-founder">
                       <span
                         class="circle-label-name"
@@ -186,7 +186,7 @@
                       type="radio"
                       name="circle"
                       value="practitioner"
-                    />
+                    >
                     <label for="circle-practitioner">
                       <span
                         class="circle-label-name"
@@ -198,90 +198,13 @@
                   </div>
                 </div>
               </div>
-              <div class="form-group">
+              <ContributionAmountField
-                <label class="form-label">Billing Cadence</label>
+                v-model="form.contributionAmount"
-                <div class="cadence-radios">
+                v-model:cadence="cadence"
-                  <div class="circle-radio">
+              />
-                    <input
-                      id="cadence-monthly"
-                      v-model="cadence"
-                      type="radio"
-                      name="cadence"
-                      value="monthly"
-                    />
-                    <label for="cadence-monthly">
-                      <span class="circle-label-name">Per Month</span>
-                    </label>
-                  </div>
-                  <div class="circle-radio">
-                    <input
-                      id="cadence-annual"
-                      v-model="cadence"
-                      type="radio"
-                      name="cadence"
-                      value="annual"
-                    />
-                    <label for="cadence-annual">
-                      <span class="circle-label-name">Per Year</span>
-                    </label>
-                  </div>
-                </div>
-              </div>
-              <div class="form-group">
-                <label class="form-label" for="join-contribution">
-                  Monthly Contribution
-                </label>
-                <div class="contribution-input-row">
-                  <span class="contribution-currency">$</span>
-                  <input
-                    id="join-contribution"
-                    v-model.number="form.contributionAmount"
-                    type="number"
-                    min="0"
-                    step="1"
-                    inputmode="numeric"
-                    class="contribution-input"
-                  />
-                </div>
-                <div
-                  class="contribution-presets"
-                  role="group"
-                  aria-label="Suggested amounts"
-                >
-                  <button
-                    v-for="preset in CONTRIBUTION_PRESETS"
-                    :key="preset.amount"
-                    type="button"
-                    class="contribution-preset-chip"
-                    @click="form.contributionAmount = preset.amount"
-                  >
-                    ${{ preset.amount }}
-                  </button>
-                </div>
-                <p v-if="guidanceLabel" class="contribution-guidance">
-                  {{ guidanceLabel }}
-                </p>
-              </div>
-              <div v-if="form.contributionAmount > 0" class="form-group">
-                <div class="billing-summary">
-                  <p class="billing-summary-line">
-                    You'll be charged <strong>${{ firstCharge }} today</strong
-                    ><span v-if="cadence === 'annual'">
-                      (${{ form.contributionAmount }}/month &times; 12)</span
-                    >.
-                  </p>
-                  <p class="billing-summary-line">
-                    Then
-                    <strong
-                      >${{ firstCharge }} every
-                      {{ cadence === "annual" ? "year" : "month" }}</strong
-                    >, until you cancel.
-                  </p>
-                </div>
-              </div>
               <div class="form-group full-width">
                 <label class="checkbox-label">
-                  <input v-model="form.agreedToGuidelines" type="checkbox" />
+                  <input v-model="form.agreedToGuidelines" type="checkbox" >
                   <span>
                     I agree to the Ghost Guild
                     <NuxtLink to="/community-guidelines" target="_blank"
@@ -385,11 +308,7 @@
 <script setup>
 import { reactive, ref, computed, onMounted, onUnmounted } from "vue";
 import { getCircleOptions } from "~/config/circles";
-import {
+import { requiresPayment } from "~/config/contributions";
-  requiresPayment,
-  CONTRIBUTION_PRESETS,
-  getGuidanceLabel,
-} from "~/config/contributions";
 
 useSiteMeta({
   title: "Join",
@@ -475,13 +394,6 @@ const needsPayment = computed(() => {
   return requiresPayment(form.contributionAmount);
 });
 
-const guidanceLabel = computed(() => getGuidanceLabel(form.contributionAmount));
-
-const firstCharge = computed(() => {
-  const amount = form.contributionAmount || 0;
-  return cadence.value === "annual" ? amount * 12 : amount;
-});
-
 const flowSummary = computed(() => ({
   name: form.name,
   email: form.email,
@@ -840,79 +752,6 @@ onUnmounted(() => {
   color: var(--text-faint);
 }
 
-/* ---- CADENCE RADIOS ---- */
-.cadence-radios {
-  display: grid;
-  grid-template-columns: repeat(2, 1fr);
-  gap: 10px;
-}
-
-/* ---- CONTRIBUTION AMOUNT INPUT + CHIPS ---- */
-.contribution-input-row {
-  display: flex;
-  align-items: center;
-  gap: 0.25rem;
-}
-.contribution-currency {
-  font-weight: 600;
-}
-.contribution-input {
-  flex: 1;
-  padding: 0.5rem 0.75rem;
-  background: var(--input-bg);
-  border: 1px solid var(--parch);
-  font-family: "Commit Mono", monospace;
-  font-size: 1rem;
-}
-.contribution-input:focus {
-  outline: none;
-  border-color: var(--candle);
-}
-.contribution-presets {
-  display: flex;
-  flex-wrap: wrap;
-  gap: 0.5rem;
-  margin-top: 0.5rem;
-}
-.contribution-preset-chip {
-  padding: 0.25rem 0.75rem;
-  background: transparent;
-  border: 1px dashed var(--parch);
-  font-family: "Commit Mono", monospace;
-  font-size: 0.875rem;
-  cursor: pointer;
-}
-.contribution-preset-chip:hover {
-  border-style: solid;
-  border-color: var(--candle);
-}
-.contribution-guidance {
-  margin-top: 0.5rem;
-  font-size: 0.875rem;
-  font-style: italic;
-  color: var(--ink-soft, currentColor);
-}
-
-/* ---- BILLING SUMMARY ---- */
-.billing-summary {
-  padding: 12px 16px;
-  border: 1px dashed var(--border);
-  background: var(--surface);
-}
-.billing-summary-line {
-  font-size: 13px;
-  color: var(--text);
-  line-height: 1.5;
-  margin: 0;
-}
-.billing-summary-line + .billing-summary-line {
-  margin-top: 4px;
-}
-.billing-summary-line strong {
-  color: var(--text-bright);
-  font-weight: 600;
-}
-
 /* ---- CIRCLE RADIOS ---- */
 .circle-radios {
   display: grid;