Implement WP-0015-T01/T04/T06: Phase provenance schema + ledger UI

Schema: phase.milestone_release gains required repo_hub/repo_hub_uri/
repo_id/repo_name; phase gains optional base_phase_id. Backfilled the
golden phase-001 fixture (placeholder values, it's synthetic) and the
three real pilot-candidate manifests with actual Forgejo repo ids
confirmed live (net-kingdom=67, vergabe-teilnahme=62,
info-tech-canon=47, all coulomb/*).

Discovered along the way: the schema change alone would have broken
the existing Control Plane registration form, since nothing collected
the four new fields. Fixed inline rather than leaving it broken
between tasks -- this also completes T04's ledger UI change (drop the
hand-typed ledger input, auto-compute /phases/{id}/ledger, add a
drill-down reference link on phase_detail.html) since both changes
touch the same form/route.

Full suite: 94 passing offline (was 84), 158 passing with Docker
(was 146).

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

src/target_revenue/service/control_plane_templates/phase_detail.html

@@ -6,6 +6,16 @@
 </wn-page-header>
 <p><wn-tag>{{ manifest.phase.id }}</wn-tag></p>
 
+<details style="margin-bottom:1rem;color:#888;font-size:0.9rem;">
+  <summary style="cursor:pointer;">Ledger reference (internal — not this Phase's ledger entries, see below)</summary>
+  <p>
+    Raw reference: <code>{{ manifest.phase.ledger }}</code>
+    {% if manifest.phase.ledger.startswith('/phases/') %}
+      &middot; <a href="{{ manifest.phase.ledger }}">view live JSON</a>
+    {% endif %}
+  </p>
+</details>
+
 <h3>Status</h3>
 <table class="wn-plain">
   <tr><td>Initial Target</td><td>{{ manifest.phase.initial_target.amount }} {{ manifest.phase.initial_target.currency }}</td></tr>