feat(web): customizable placeholder, footer text, and color theme via BOR_* env vars

BOR_INPUT_PLACEHOLDER / BOR_FOOTER_TEXT / BOR_THEME (+ the indigo.css example theme); authoring guide: frontend/assets/themes/README.md, docs: README 'Customizing the look'.

tests/integration/test_api.py

@@ -18,16 +18,26 @@ def test_health_reports_ok(client) -> None:
 
 
 def test_config_returns_default_app_metadata(client) -> None:
-    """GET /api/config is public (anonymous) and returns exactly three
-    keys — the phase-39 app metadata + the phase-59 docs flag (inert
-    false while BOR_DOCS_REPO is empty — the "Save as doc" gating)."""
+    """GET /api/config is public (anonymous) and returns exactly six
+    keys — the phase-39 app metadata, the phase-59 docs flag (inert
+    false while BOR_DOCS_REPO is empty — the "Save as doc" gating),
+    and the phase-62 UI customization strings (composer placeholder,
+    footer line, theme file name)."""
     r = client.get("/api/config")
     assert r.status_code == 200
     body = r.json()
-    assert set(body) == {"app_name", "version", "docs_repo_configured"}
+    assert set(body) == {
+        "app_name", "version", "docs_repo_configured",
+        "input_placeholder", "footer_text", "theme",
+    }
     assert body["app_name"] == "Brain of Reese"
     assert body["version"] == get_settings().app_version
     assert body["docs_repo_configured"] is False
+    # Phase 62: UNSET => the phase-61 neutral copy stands (the
+    # byte-identical contract); an empty theme = the built-in palette.
+    assert body["input_placeholder"] == "Ask me anything…"
+    assert body["footer_text"] == "Powered by self-hosted models"
+    assert body["theme"] == ""
 
 
 def test_config_follows_overridden_app_name(client) -> None:
@@ -42,7 +52,10 @@ def test_config_follows_overridden_app_name(client) -> None:
         r = client.get("/api/config")
         assert r.status_code == 200
         body = r.json()
-        assert set(body) == {"app_name", "version", "docs_repo_configured"}
+        assert set(body) == {
+            "app_name", "version", "docs_repo_configured",
+            "input_placeholder", "footer_text", "theme",
+        }
         assert body["app_name"] == "Brain of Testy"
         assert body["version"] == "0.1.0"
         assert body["docs_repo_configured"] is False
@@ -50,6 +63,34 @@ def test_config_follows_overridden_app_name(client) -> None:
         fastapi_app.dependency_overrides.clear()
 
 
+def test_config_serves_ui_customization_overrides(client) -> None:
+    """Phase 62: the three UI customization keys mirror Settings
+    overrides (``BOR_INPUT_PLACEHOLDER`` / ``BOR_FOOTER_TEXT`` /
+    ``BOR_THEME``) verbatim — the values the frontend brand layer
+    applies at boot, so this dict is the whole contract."""
+    from app.config import Settings
+    from app.main import app as fastapi_app
+
+    fastapi_app.dependency_overrides[get_settings] = lambda: Settings(
+        input_placeholder="Ask the vault…",
+        footer_text="Powered by my own models",
+        theme="indigo.css",
+    )
+    try:
+        r = client.get("/api/config")
+        assert r.status_code == 200
+        body = r.json()
+        assert set(body) == {
+            "app_name", "version", "docs_repo_configured",
+            "input_placeholder", "footer_text", "theme",
+        }
+        assert body["input_placeholder"] == "Ask the vault…"
+        assert body["footer_text"] == "Powered by my own models"
+        assert body["theme"] == "indigo.css"
+    finally:
+        fastapi_app.dependency_overrides.clear()
+
+
 def test_config_docs_flag_tracks_settings(client) -> None:
     """Phase 59 (task 05): ``docs_repo_configured`` mirrors
     ``settings.docs_configured`` — a real bool (never a truthy string)