M1 step 3: Log writing and Storage Clean-up

- lib/storage_model (host-tested): FAT-safe names, daily Log paths,
  dates from Log/Capture file names, CleanupPlan by category and age,
  byte formatting
- StorageService does all card I/O on its task: queued Log lines are
  written in batches each second (dropped while Logs are paused),
  plus file listing and deletion jobs
- Settings > Storage moves into StoragePage: usage, Clean up
  (category, age with size preview, confirmation), Erase SD card
- Clock: local date for Log names
- Serial: log <text>, sd list

Verified on the device: lines land in /irc/dev/#test/2026-10-02.log
with folders created as needed.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01EhqxQ49eCju4CzKYNjZzwT

lib/storage_model/src/cleanup_plan.h

@@ -0,0 +1,40 @@
+#pragma once
+
+#include <cstdint>
+#include <string>
+#include <vector>
+
+namespace roro {
+
+struct StoredFile {
+    std::string path;
+    uint64_t bytes;
+};
+
+// What Storage Clean-up offers (see CONTEXT.md). Notes are deliberately absent.
+struct CleanupCategory {
+    const char* label;
+    const char* folder;
+};
+inline const CleanupCategory kCleanupCategories[] = {
+    {"IRC logs", "/irc"},
+    {"Probe-request logs", "/wifi/probes"},
+    {"Wi-Fi captures", "/captures/wifi"},
+};
+
+enum class CleanupAge { OneMonth, ThreeMonths, SixMonths, OneYear, Everything };
+inline const char* const kCleanupAgeLabels[] = {"Older than 1 month", "Older than 3 months", "Older than 6 months",
+                                                "Older than 1 year", "Everything"};
+
+// The files a clean-up would delete, and how much space that frees. Dates come from file names;
+// undated files are only removed by Everything.
+struct CleanupPlan {
+    std::vector<std::string> paths;
+    uint64_t bytes = 0;
+
+    static CleanupPlan make(const std::vector<StoredFile>& files, CleanupAge age, int todayDay);
+};
+
+std::string formatBytes(uint64_t bytes);
+
+}  // namespace roro