fix(settings): app fails to launch on real hardware — misaligned relocation from packed struct pointer

[vvzvlad]

Problem

On real hardware (Pebble Time 2 / emery) TimelyNG never launches — selecting
it drops straight back to the launcher. The firmware log shows:

[WARN] process_loader_storage.c:162  Invalid app relocation target[68]: 0x78d7
[WARN] app_manager.c:315             Tried to launch an invalid app in bank 6!
[WARN] app_manager.c:629             Failed to start app <TimelyNG>! Restarting launcher

So the app is rejected at load time, during relocation fix-up — it is not a
heap or SDK-version problem (heap is ~99 KB free, sdk_version 5.104 matches).

Root cause

persist in src/settings.h is __attribute__((__packed__)) and contains a
pointer member:

typedef struct persist {
  uint8_t version;              // 18 single-byte fields (offsets 0..17)
  ...
  uint8_t vibe_pat_connect;
  char *strftime_format;        // pointer at unaligned offset 18
  ...
} __attribute__((__packed__)) persist;

Because the struct is packed, strftime_format lands at byte offset 18. The
static initialiser in src/settings.c set it to a string literal:

.strftime_format = "%Y-%m-%d",

That stores an absolute address, so the toolchain emits an R_ARM_ABS32
relocation at image offset 0x78d7 (= &s_settings + 18), which is not
word-aligned. prv_apply_relocations() in the app loader requires every
relocation target to be word-aligned and rejects the whole app when it isn't —
hence "Invalid app relocation target" and the app never runs.

This likely doesn't reproduce in every emulator/SDK (older loaders didn't
enforce the alignment check), which is why it slipped through, but the current
Core Devices firmware enforces it.

Fix

persist.strftime_format is never read in C — the custom date format used at
runtime is adv_settings.custom_date_fmt (Timely.c, date_format == 255).
So initialise the field to a null pointer instead of a literal:

.strftime_format = 0,

A null pointer needs no relocation, so the offending R_ARM_ABS32 entry
disappears. The struct layout is unchanged, so persist_read_data /
persist_write_data stay byte-compatible with existing installs.

Verification

• Rebuilt for emery: relocation count drops 76 → 75, and every remaining
  entry is word-aligned and in range (previously entry 68 = 0x78d7).
• Installed the rebuilt .pbw on a real Pebble Time 2 and confirmed the
  watchface launches and stays running (app run state: RUNNING,
  no "invalid app" / no fault loop).

🤖 Generated with Claude Code