feat(dashboard): functions explorer + top-level tabs + pie chart fit

- Pie charts (Purity, Kind) ahora reciben plot_h explicito para que respeten
  el panel contenedor y no desborden cuando la ventana se reduce.
- Nueva pestana "Explorer": split layout con lista filtrable a la izquierda
  (search por nombre/descripcion + combos lang/domain) y panel de detalle
  a la derecha con tabs Code (read-only multiline), Documentation (selectable
  text), Tests (con dropdown si la funcion tiene varios tests, muestra lang +
  file_path + codigo) y Metadata (id, version, file_path, returns,
  uses_functions, uses_types, params_schema, example, notes).
- Reorganizacion de navegacion: TabBar movido arriba, justo debajo de la
  toolbar. Tabs: Dashboard | Explorer | Projects | Apps | Analysis | Types.
  Cada tab ocupa toda la zona de contenido. Dashboard incluye KPIs + charts
  + tabla de Recent Functions.
- Cache del Explorer (lista de funciones) invalidado en trigger_reload.
- Nuevas funciones HTTP: load_function_detail_http, load_all_functions_http,
  load_unit_tests_http (todas usan /api/databases/registry/query con escape
  defensivo de comilla simple en IDs).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

data_http.cpp

@@ -308,6 +308,130 @@ bool load_project_detail_http(const std::string& api_url,
     return true;
 }
 
+// ---------------------------------------------------------------------------
+// Function detail endpoints (Explorer)
+// ---------------------------------------------------------------------------
+
+bool load_function_detail_http(const std::string& api_url,
+                               const std::string& id,
+                               FunctionDetail& out) {
+    std::string host; int port;
+    if (!parse_url(api_url, host, port)) return false;
+
+    HttpClient cli(host, port);
+
+    // /api/databases/<db>/query solo acepta { "sql": ... } sin args
+    // parametrizados (ver handleQuery en sqlite_api). Escapamos comilla
+    // simple para que un id con apostrofe no rompa la query — los IDs del
+    // registry son [a-z0-9_]+ asi que el escape es defensivo.
+    std::string escaped;
+    escaped.reserve(id.size());
+    for (char c : id) {
+        if (c == '\'') escaped += "''";
+        else escaped.push_back(c);
+    }
+    std::string sql =
+        "SELECT id, name, lang, domain, kind, purity, version, signature, "
+        "description, code, documentation, notes, example, params_schema, "
+        "uses_functions, uses_types, returns, error_type, file_path, "
+        "created_at, tested FROM functions WHERE id = '" + escaped + "'";
+
+    auto j = api_query(cli, sql.c_str());
+    if (j.is_null() || !j.contains("rows") || j["rows"].empty()) return false;
+
+    auto& row = j["rows"][0];
+    out = FunctionDetail{};
+    out.id            = extract_str(row, 0);
+    out.name          = extract_str(row, 1);
+    out.lang          = extract_str(row, 2);
+    out.domain        = extract_str(row, 3);
+    out.kind          = extract_str(row, 4);
+    out.purity        = extract_str(row, 5);
+    out.version       = extract_str(row, 6);
+    out.signature     = extract_str(row, 7);
+    out.description   = extract_str(row, 8);
+    out.code          = extract_str(row, 9);
+    out.documentation = extract_str(row, 10);
+    out.notes         = extract_str(row, 11);
+    out.example       = extract_str(row, 12);
+    out.params_schema = extract_str(row, 13);
+    out.uses_functions= extract_str(row, 14);
+    out.uses_types    = extract_str(row, 15);
+    out.returns       = extract_str(row, 16);
+    out.error_type    = extract_str(row, 17);
+    out.file_path     = extract_str(row, 18);
+    out.created_at    = extract_str(row, 19);
+    out.tested        = extract_row_int(row, 20) != 0;
+    return true;
+}
+
+bool load_all_functions_http(const std::string& api_url,
+                             std::vector<FunctionRow>& out) {
+    std::string host; int port;
+    if (!parse_url(api_url, host, port)) return false;
+
+    HttpClient cli(host, port);
+    auto j = api_query(cli,
+        "SELECT id, name, lang, domain, kind, purity, description, "
+        "created_at, tested FROM functions ORDER BY name");
+    if (j.is_null() || !j.contains("rows")) return false;
+
+    out.clear();
+    out.reserve(j["rows"].size());
+    for (auto& row : j["rows"]) {
+        FunctionRow r;
+        r.id = extract_str(row, 0);
+        r.name = extract_str(row, 1);
+        r.lang = extract_str(row, 2);
+        r.domain = extract_str(row, 3);
+        r.kind = extract_str(row, 4);
+        r.purity = extract_str(row, 5);
+        r.description = extract_str(row, 6);
+        r.created_at = extract_str(row, 7);
+        r.tested = extract_row_int(row, 8) != 0;
+        out.push_back(std::move(r));
+    }
+    return true;
+}
+
+bool load_unit_tests_http(const std::string& api_url,
+                          const std::string& function_id,
+                          std::vector<UnitTestRow>& out) {
+    std::string host; int port;
+    if (!parse_url(api_url, host, port)) return false;
+
+    HttpClient cli(host, port);
+
+    // Mismo escape defensivo que en load_function_detail_http — los IDs son
+    // [a-z0-9_]+ pero por consistencia escapamos comilla simple.
+    std::string escaped;
+    escaped.reserve(function_id.size());
+    for (char c : function_id) {
+        if (c == '\'') escaped += "''";
+        else escaped.push_back(c);
+    }
+    std::string sql =
+        "SELECT id, function_id, name, lang, file_path, code, created_at "
+        "FROM unit_tests WHERE function_id = '" + escaped + "' ORDER BY name";
+
+    auto j = api_query(cli, sql.c_str());
+    if (j.is_null() || !j.contains("rows")) return false;
+
+    out.clear();
+    for (auto& row : j["rows"]) {
+        UnitTestRow r;
+        r.id          = extract_str(row, 0);
+        r.function_id = extract_str(row, 1);
+        r.name        = extract_str(row, 2);
+        r.lang        = extract_str(row, 3);
+        r.file_path   = extract_str(row, 4);
+        r.code        = extract_str(row, 5);
+        r.created_at  = extract_str(row, 6);
+        out.push_back(std::move(r));
+    }
+    return true;
+}
+
 // ---------------------------------------------------------------------------
 // Mutation endpoints
 // ---------------------------------------------------------------------------