Add official US and European collection and calendar storage

Collect official RSS and Atom summaries, preserve historical captures, and poll macro releases with bounded cadence and Retry-After handling. Separate news collectors from the economic calendar worker.

Track statistical periods, publication stages, first observations, revisions, and current official series. Include explicit migration files and isolated archive, parsing, and import tests; no migration or import is executed by this commit.

Keep dependency declarations and lockfile together for PDF archives and the upcoming captcha integration. Verify the staged snapshot with 90 focused tests.

backend/tests/fixtures/europe/boe_schedule.html

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+<html><body><div class="page-content" data-id="f63a0ea5089d4b1a9d8f2c10bb711c1e">
+            <h2>2026 confirmed dates</h2>
+<table>
+    <tbody>
+        <tr>
+            <td>Thursday 5 February</td>
+            <td><a href="/monetary-policy-summary-and-minutes/2026/february-2026">February MPC Summary and minutes</a> and <a href="/monetary-policy-report/2026/february-2026">February Monetary Policy Report</a></td>
+        </tr>
+        <tr>
+            <td>Thursday 19 March</td>
+            <td><a href="/monetary-policy-summary-and-minutes/2026/march-2026">March MPC Summary and minutes</a></td>
+        </tr>
+        <tr>
+            <td>Thursday 30 April</td>
+            <td><a href="/monetary-policy-summary-and-minutes/2026/april-2026">April MPC Summary and minutes</a> and <a href="/monetary-policy-report/2026/april-2026">April Monetary Policy Report</a></td>
+        </tr>
+        <tr>
+            <td>Thursday 18 June</td>
+            <td><a href="/monetary-policy-summary-and-minutes/2026/june-2026">June MPC Summary and minutes</a></td>
+        </tr>
+        <tr>
+            <td>Thursday 30 July</td>
+            <td><a href="/monetary-policy-summary-and-minutes/2026/july-2026">July MPC Summary and minutes</a> and <a href="/monetary-policy-report/2026/july-2026">July Monetary Policy Report</a></td>
+        </tr>
+        <tr>
+            <td>Thursday 17 September</td>
+            <td><a href="/monetary-policy-summary-and-minutes/2026/september-2026">September MPC Summary and minutes</a></td>
+        </tr>
+        <tr>
+            <td>Thursday 5 November</td>
+            <td><a href="/monetary-policy-summary-and-minutes/2026/november-2026">November MPC Summary and minutes</a> and <a href="/monetary-policy-report/2026/november-2026">November Monetary Policy Report</a></td>
+        </tr>
+        <tr>
+            <td>Thursday 17 December</td>
+            <td><a href="/monetary-policy-summary-and-minutes/2026/december-2026">December MPC Summary and minutes</a></td>
+        </tr>
+    </tbody>
+</table>
+        </div><div class="page-content" data-id="a3c1a1b2a7904eab8f2285efacdc6eb6">
+            <h2>2027 confirmed dates</h2>
+<table>
+    <tbody>
+        <tr>
+            <td>Thursday 4 February</td>
+            <td><span style="background-color: #f6f6f6;"><a href="/monetary-policy-summary-and-minutes/2027/february-2027">February MPC Summary and minutes</a> and <a href="/monetary-policy-report/2027/february-2027">February Monetary Policy Report</a> </span> </td>
+        </tr>
+        <tr>
+            <td>Thursday 18 March </td>
+            <td><span style="background-color: #f6f6f6;"><a href="/monetary-policy-summary-and-minutes/2027/march-2027">March MPC Summary and minutes</a></span> </td>
+        </tr>
+        <tr>
+            <td>Thursday 29 April</td>
+            <td><span style="background-color: #f6f6f6;"><a href="/monetary-policy-summary-and-minutes/2027/april-2027">April MPC Summary and minutes</a> and <a href="/monetary-policy-report/2027/april-2027">April Monetary Policy Report</a> </span> </td>
+        </tr>
+        <tr>
+            <td>Thursday 17 June </td>
+            <td><span style="background-color: #f6f6f6;"><a href="/monetary-policy-summary-and-minutes/2027/june-2027">June MPC Summary and minutes</a></span> </td>
+        </tr>
+        <tr>
+            <td>Thursday 29 July </td>
+            <td><span style="background-color: #f6f6f6;"><a href="/monetary-policy-summary-and-minutes/2027/july-2027">July MPC Summary and minutes</a> and <a href="/monetary-policy-report/2027/july-2027">July Monetary Policy Report</a> </span> </td>
+        </tr>
+        <tr>
+            <td>Thursday 16 September  </td>
+            <td><span style="background-color: #f6f6f6;"><a href="/monetary-policy-summary-and-minutes/2027/september-2027">September MPC Summary and minutes</a></span> </td>
+        </tr>
+        <tr>
+            <td>Thursday 4 November </td>
+            <td><span><a href="/monetary-policy-summary-and-minutes/2027/november-2027">November MPC Summary and minutes</a> and <a href="/monetary-policy-report/2027/november-2027">November Monetary Policy Report</a> </span> </td>
+        </tr>
+        <tr>
+            <td>Thursday 16 December </td>
+            <td><span style="background-color: #f6f6f6;"><a href="/monetary-policy-summary-and-minutes/2027/december-2027">December MPC Summary and minutes</a></span> </td>
+        </tr>
+    </tbody>
+</table>
+        </div></body></html>