chore(13e6): TEMP power-monitor telemetry headers

To validate the PIN_PWR rail-cut change (e2c9d8f) without a bench
multimeter, have the device report its previous cycle's awake time
and panel-init time on each poll:

  X-Prev-Awake-Ms       — millis() at the moment esp_deep_sleep_start
                          armed, last cycle. Total awake duration
                          since reset, ~5–10 s steady-state.
  X-Prev-Panel-Init-Ms  — duration of epd_init() last cycle. Spikes
                          here would suggest the rail isn't coming
                          back up cleanly after the GPIO-hold release.

Headers are sent only when the cached NVS values are non-zero (skips
the first boot under this firmware). All call sites marked `// TEMP:
power-monitor` for clean removal once the change is validated. Two
new NVS keys (tm_awk, tm_pin) sit alongside the existing ones; mock
Preferences extended with getUInt/putUInt to match.

Server side logs the headers via `device.poll.power_telemetry`
(separate commit in pictureFrame-webApp).

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

src/config.h

@@ -117,6 +117,13 @@
 // would silently keep displaying the prior owner's photos until the new
 // owner happens to navigate to /setup/{mac}.
 #define NVS_KEY_JUST_PROVISIONED "just_prov"
+// TEMP: power-monitor — stores previous cycle's awake duration and
+// epd_init() duration so the next boot can report them server-side as
+// X-Prev-Awake-Ms / X-Prev-Panel-Init-Ms. Lets us verify PIN_PWR rail
+// cut doesn't slow panel re-init or extend the awake window. Remove
+// these keys + their reads/writes once the change is validated.
+#define NVS_KEY_PREV_AWAKE_MS      "tm_awk"
+#define NVS_KEY_PREV_PANEL_INIT_MS "tm_pin"
 
 // Bump when introducing a schema migration. Each new value can force a one-shot
 // recovery action on first boot of the new firmware.

src/operation.h

@@ -116,6 +116,12 @@ void normal_operation_impl(const String& mac, HTTP& http, const String& url, Pre
     bool errBorder  = prefs.getInt(NVS_KEY_ERR_BORDER, 0) != 0;
     int  schemaV    = prefs.getInt(NVS_KEY_SCHEMA_V, 0);
     bool justProvisioned = prefs.getInt(NVS_KEY_JUST_PROVISIONED, 0) != 0;
+    // TEMP: power-monitor — previous cycle's awake + panel-init durations.
+    // Reported as X-Prev-Awake-Ms / X-Prev-Panel-Init-Ms below. Remove
+    // along with the corresponding writes near deep_sleep_start + the
+    // epd_init() timing block once the PIN_PWR cut is validated.
+    uint32_t prevAwakeMs     = prefs.getUInt(NVS_KEY_PREV_AWAKE_MS, 0);
+    uint32_t prevPanelInitMs = prefs.getUInt(NVS_KEY_PREV_PANEL_INIT_MS, 0);
     prefs.end();
 
     // Schema migration: on first boot under err-border-aware firmware, the
@@ -162,6 +168,17 @@ void normal_operation_impl(const String& mac, HTTP& http, const String& url, Pre
         http.addHeader("X-Just-Provisioned", "1");
     }
 
+    // TEMP: power-monitor — last cycle's awake + panel-init times.
+    // Lets us see, server-side, whether the PIN_PWR rail cut affects
+    // either. Send only if non-zero (skips the first boot after a
+    // firmware that didn't store them).
+    if (prevAwakeMs > 0) {
+        http.addHeader("X-Prev-Awake-Ms", String((unsigned long)prevAwakeMs));
+    }
+    if (prevPanelInitMs > 0) {
+        http.addHeader("X-Prev-Panel-Init-Ms", String((unsigned long)prevPanelInitMs));
+    }
+
     const char* collectHeaders[] = { "X-Interval-Ms", "X-Image-Id", "X-Image-Sha256", "X-Claimed" };
     http.collectHeaders(collectHeaders, 4);
     int code = http.GET();
@@ -244,7 +261,12 @@ void normal_operation_impl(const String& mac, HTTP& http, const String& url, Pre
             }
 
             displayInitialized = true;
+            // TEMP: power-monitor — time the panel init, stored in NVS at
+            // end of cycle for next boot to report. Remove the timing
+            // wrapper when the PIN_PWR cut is validated.
+            uint32_t panelInitStart = millis();
             epd_init();
+            uint32_t panelInitMs = millis() - panelInitStart;
             File r = LittleFS.open(IMAGE_PATH, "r");
             if (r) { epd_draw_image_from_file(r); r.close(); }
 
@@ -253,6 +275,7 @@ void normal_operation_impl(const String& mac, HTTP& http, const String& url, Pre
             prefs.begin(NVS_NAMESPACE, false);
             prefs.putInt(NVS_KEY_DRAW_NEEDED, 0);
             prefs.putInt(NVS_KEY_ERR_BORDER, 0);
+            prefs.putUInt(NVS_KEY_PREV_PANEL_INIT_MS, panelInitMs);  // TEMP
             prefs.end();
         }
 
@@ -362,6 +385,14 @@ void normal_operation_impl(const String& mac, HTTP& http, const String& url, Pre
     // up, losing the saving. Released per-pin in epd_setup_pins() on
     // wake via gpio_hold_dis().
     gpio_deep_sleep_hold_en();
+
+    // TEMP: power-monitor — millis() at this point is the total awake
+    // duration since boot. Next boot reads it back and reports as
+    // X-Prev-Awake-Ms. Remove when PIN_PWR cut is validated.
+    prefs.begin(NVS_NAMESPACE, false);
+    prefs.putUInt(NVS_KEY_PREV_AWAKE_MS, millis());
+    prefs.end();
+
     esp_deep_sleep_start();
 }
 

test/mocks/Preferences.h

@@ -8,6 +8,7 @@ extern int g_prefs_putint_seq;  // sequence position of last putInt call
 
 struct Preferences {
     std::map<std::string, int32_t>  ints;
+    std::map<std::string, uint32_t> uints;
     std::map<std::string, std::string> strings;
     bool _open = false;
 
@@ -26,10 +27,16 @@ struct Preferences {
         g_call_seq++;
     }
 
+    uint32_t getUInt(const char* key, uint32_t def = 0) {
+        auto it = uints.find(key);
+        return it != uints.end() ? it->second : def;
+    }
+    void putUInt(const char* key, uint32_t val) { uints[key] = val; }
+
     String getString(const char* key, const char* def = "") {
         auto it = strings.find(key);
         return it != strings.end() ? String(it->second) : String(def);
     }
     void putString(const char* key, const String& val) { strings[key] = val._s; }
-    void clear() { ints.clear(); strings.clear(); }
+    void clear() { ints.clear(); uints.clear(); strings.clear(); }
 };