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>

schemas/phase_manifest.schema.json

@@ -35,7 +35,7 @@
         },
         "milestone_release": {
           "type": "object",
-          "required": ["name", "source_revision"],
+          "required": ["name", "source_revision", "repo_hub", "repo_hub_uri", "repo_id", "repo_name"],
           "additionalProperties": false,
           "properties": {
             "name": { "type": "string" },
@@ -44,6 +44,26 @@
               "type": "string",
               "pattern": "^[a-f0-9]{64}$",
               "description": "Recommended; required if a built artifact (not just source) is governed."
+            },
+            "repo_hub": {
+              "type": "string",
+              "pattern": "^[a-z0-9-]+$",
+              "description": "Stable, human-assigned slug for the Forgejo instance hosting this repo, e.g. \"forgejo-coulomb\". Minted by this project, not read from Forgejo (no instance-level identity endpoint exists)."
+            },
+            "repo_hub_uri": {
+              "type": "string",
+              "format": "uri",
+              "description": "The Forgejo service's current base URL, e.g. \"https://forgejo.coulomb.social\". Retained alongside repo_hub (not derived from it) so a domain change stays repairable."
+            },
+            "repo_id": {
+              "type": "integer",
+              "minimum": 1,
+              "description": "Forgejo's own internal numeric repo id (GET /api/v1/repos/{owner}/{repo} -> id). Stable across repo renames, unlike repo_name."
+            },
+            "repo_name": {
+              "type": "string",
+              "pattern": "^[\\w.-]+/[\\w.-]+$",
+              "description": "\"owner/repo\" slug at time of Phase registration. Human-readable; repo_id is authoritative if this ever diverges after a rename."
             }
           }
         },
@@ -93,6 +113,11 @@
         "ledger": {
           "type": "string",
           "description": "URL or relative path URI to the authoritative Target Ledger for this Phase."
+        },
+        "base_phase_id": {
+          "type": "string",
+          "pattern": "^trsl:phase:[a-zA-Z0-9._-]+$",
+          "description": "The prior Phase this one succeeds (FR-11, Rule 7). Absent for a repo's first-ever Phase; no sentinel value is used."
         }
       }
     },