Phase 0/2: API layer kept 1:1, only secrets.h include path fixed

http_client/weather_api/calendar_api/departures_api are hardware-
independent (HTTP GET + ArduinoJson parsing, same endpoints, same
JSON). Kept verbatim per PLAN.md migration strategy; only changed
#include "../../include/secrets.h" -> #include <secrets.h> to match
the PlatformIO include/ layout (no functional change).

src/api/calendar_api.cpp

@@ -0,0 +1,27 @@
+#include "calendar_api.h"
+#include "http_client.h"
+#include <secrets.h>
+#include <ArduinoJson.h>
+
+CalendarData fetchCalendar() {
+    CalendarData data;
+    ApiResult res = httpGet(CALENDAR_API_URL);
+    if (!res.success) { data.valid = false; return data; }
+
+    DynamicJsonDocument doc(8192);
+    if (deserializeJson(doc, res.body)) { data.valid = false; return data; }
+
+    JsonArray events = doc["events"];
+    for (JsonObject e : events) {
+        CalendarEvent ev;
+        ev.id = e["id"] | 0;
+        ev.summary = e["summary"] | "";
+        ev.startAt = e["start_at"] | "";
+        ev.endAt = e["end_at"] | "";
+        ev.allDay = e["all_day"] | false;
+        ev.status = e["status"] | "";
+        data.events.push_back(ev);
+    }
+    data.valid = true;
+    return data;
+}

src/api/calendar_api.h

@@ -0,0 +1,19 @@
+#pragma once
+#include <Arduino.h>
+#include <vector>
+
+struct CalendarEvent {
+    long id = 0;
+    String summary;
+    String startAt;
+    String endAt;
+    bool allDay = false;
+    String status;
+};
+
+struct CalendarData {
+    bool valid = false;
+    std::vector<CalendarEvent> events;
+};
+
+CalendarData fetchCalendar();

src/api/departures_api.cpp

@@ -0,0 +1,30 @@
+#include "departures_api.h"
+#include "http_client.h"
+#include <secrets.h>
+#include <ArduinoJson.h>
+
+DeparturesData fetchDepartures() {
+    DeparturesData data;
+    ApiResult res = httpGet(DEPARTURES_API_URL);
+    if (!res.success) { data.valid = false; return data; }
+
+    DynamicJsonDocument doc(16384);
+    if (deserializeJson(doc, res.body)) { data.valid = false; return data; }
+
+    JsonArray departures = doc["departures"];
+    for (JsonObject d : departures) {
+        Departure dep;
+        dep.station = d["station"] | "";
+        dep.type = d["type"] | "";
+        dep.icon = d["icon"] | "";
+        dep.line = d["line"] | "";
+        dep.destination = d["destination"] | "";
+        dep.timeEpoch = d["time_epoch"] | 0;
+        dep.timeStr = d["time_str"] | "";
+        dep.delayMin = d["delay_min"] | 0;
+        dep.cancelled = d["cancelled"] | false;
+        data.departures.push_back(dep);
+    }
+    data.valid = true;
+    return data;
+}

src/api/departures_api.h

@@ -0,0 +1,22 @@
+#pragma once
+#include <Arduino.h>
+#include <vector>
+
+struct Departure {
+    String station;
+    String type;
+    String icon;
+    String line;
+    String destination;
+    long timeEpoch = 0;
+    String timeStr;
+    int delayMin = 0;
+    bool cancelled = false;
+};
+
+struct DeparturesData {
+    bool valid = false;
+    std::vector<Departure> departures;
+};
+
+DeparturesData fetchDepartures();

src/api/http_client.cpp

@@ -0,0 +1,25 @@
+#include "http_client.h"
+#include <HTTPClient.h>
+#include <WiFi.h>
+
+ApiResult httpGet(const String &url, uint32_t timeoutMs) {
+    ApiResult result;
+    if (WiFi.status() != WL_CONNECTED) {
+        result.success = false;
+        result.httpCode = -1;
+        return result;
+    }
+    HTTPClient http;
+    http.setTimeout(timeoutMs);
+    http.begin(url);
+    int code = http.GET();
+    result.httpCode = code;
+    if (code == HTTP_CODE_OK) {
+        result.body = http.getString();
+        result.success = true;
+    } else {
+        result.success = false;
+    }
+    http.end();
+    return result;
+}

src/api/http_client.h

@@ -0,0 +1,10 @@
+#pragma once
+#include <Arduino.h>
+
+struct ApiResult {
+    bool success = false;
+    String body;
+    int httpCode = -1;
+};
+
+ApiResult httpGet(const String &url, uint32_t timeoutMs = 5000);

src/api/weather_api.cpp

@@ -0,0 +1,44 @@
+#include "weather_api.h"
+#include "http_client.h"
+#include <secrets.h>
+#include <ArduinoJson.h>
+
+WeatherData fetchWeather() {
+    WeatherData data;
+    ApiResult res = httpGet(WEATHER_API_URL);
+    if (!res.success) { data.valid = false; return data; }
+
+    DynamicJsonDocument doc(8192);
+    if (deserializeJson(doc, res.body)) { data.valid = false; return data; }
+
+    JsonObject current = doc["current"];
+    data.current.temperature = current["temperature"] | 0;
+    data.current.symbol = current["symbol"] | "";
+    data.current.description = current["description"] | "";
+
+    JsonArray forecast = doc["forecast"];
+    for (JsonObject entry : forecast) {
+        ForecastEntry fe;
+        fe.time = entry["time"] | "";
+        fe.temperature = entry["temperature"] | 0;
+        fe.symbol = entry["symbol"] | "";
+        fe.description = entry["description"] | "";
+        JsonObject precip = entry["precipitation"];
+        fe.precipitationProbability = precip["probability"] | 0.0f;
+        fe.precipitationType = precip["type"] | "";
+        data.forecast.push_back(fe);
+    }
+    data.valid = true;
+    return data;
+}
+
+bool willRainSoon(const WeatherData &data, int hours) {
+    if (!data.valid) return false;
+    int checked = 0;
+    for (const auto &entry : data.forecast) {
+        if (checked >= hours) break;
+        if (entry.precipitationType == "rain" && entry.precipitationProbability > 0.0f) return true;
+        checked++;
+    }
+    return false;
+}

src/api/weather_api.h

@@ -0,0 +1,27 @@
+#pragma once
+#include <Arduino.h>
+#include <vector>
+
+struct WeatherCurrent {
+    int temperature = 0;
+    String symbol;
+    String description;
+};
+
+struct ForecastEntry {
+    String time;
+    int temperature = 0;
+    String symbol;
+    String description;
+    float precipitationProbability = 0.0f;
+    String precipitationType;
+};
+
+struct WeatherData {
+    bool valid = false;
+    WeatherCurrent current;
+    std::vector<ForecastEntry> forecast;
+};
+
+WeatherData fetchWeather();
+bool willRainSoon(const WeatherData &data, int hours = 8);