Places map: city base map, cluster gallery, zoom + render polish

Base map / tiles:
- Switch the base map to the mapchart city-label world map; re-derive its
  Web-Mercator georeferencing (MAP_LON0/1, MAP_IMG_MY0/1) by least-squares
  against the pixel-identical graticule export.
- Add a 1.5x LANCZOS supersample LOD and bump tile quality 90->94 so city
  labels stay crisp when zoomed in (tools/png_to_tiles.py).
- Fill the map view background with the ocean colour instead of black.

Navigation / clustering:
- Snap the cluster grid to power-of-two zoom octaves so the bubbles stop
  jittering during a continuous zoom.
- Replace the loose zoom clamps with named MAP_SCALE_MIN/MAX (whole map fills
  the screen .. country/region level).
- Add a toggleable computed lat/lon graticule overlay (TRIANGLE).

Cluster gallery:
- Selecting a bubble now opens all its photos on the same justified grid as
  the timeline/search (a g_gallery_active filter). Members not already paged
  in are appended as hidden g_asset entries (kept out of the main timeline);
  a background metadata worker resolves each one's date/aspect so the grid
  reflows into month sections + true aspect ratios.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_011uKJQMYDE9Nrq9ECsU3MxH

src/state.c

@@ -63,6 +63,29 @@ static int g_sect_count;
 static int g_sect_cap;
 static float g_content_h; /* total scrollable height incl. headers */
 
+/* map cluster gallery: the photos of one map bubble, shown on the SAME grid as
+ * the timeline/search — a filtered view like g_search_*. g_gallery_idx holds
+ * indices into the g_asset_* arrays for the bubble's members; members not
+ * already paged into the library are appended as g_asset entries flagged
+ * g_asset_hidden (so they appear only here, never in the main timeline). Their
+ * date/aspect are resolved lazily by the metadata worker below, so the grid
+ * reflows into real month sections + true aspect ratios as they arrive. */
+static int g_gallery_active;
+static int *g_gallery_idx;
+static int g_gallery_count;
+static int g_gallery_cap;
+
+/* background metadata resolver: a one-slot handoff (mirroring the thumb worker)
+ * that fetches one asset's date/aspect so the justified grid can place it. */
+enum { META_IDLE, META_PENDING, META_DONE };
+static volatile int g_meta_state = META_IDLE;
+static char g_meta_id[40];           /* asset id to resolve  (main -> worker) */
+static int g_meta_target;            /* g_asset index to fill (main-thread owned) */
+static char g_meta_date[DATELEN];    /* results (worker -> main) */
+static float g_meta_ratio;
+static unsigned char g_meta_rot;
+static int g_meta_is_video;
+
 /* free-text smart (CLIP) search. when active the grid shows only the matching
  * server assets — still date-grouped under month headers like the timeline —
  * instead of the full merged library; TRIANGLE opens the keyboard, CIRCLE (or
@@ -159,6 +182,7 @@ static int grow_assets(int need)
 	    !GROW(g_asset_rot, c, need) ||
 	    !GROW(g_asset_is_video, c, need) ||
 	    !GROW(g_asset_local_backed, c, need) ||
+	    !GROW(g_asset_hidden, c, need) ||
 	    !GROW(g_thumb, c, need) ||
 	    !GROW(g_thumb_failed, c, need) ||
 	    !(g_asset_cap = GROW(g_tex_err, c, need)))
@@ -214,6 +238,17 @@ static int grow_sect(int need)
 	return 1;
 }
 
+static int grow_gallery(int need)
+{
+	if (need <= g_gallery_cap)
+		return 1;
+	int cap = GROW(g_gallery_idx, g_gallery_cap, need);
+	if (!cap)
+		return 0;
+	g_gallery_cap = cap;
+	return 1;
+}
+
 static void log_line(const char *fmt, ...)
 {
 	FILE *f = fopen(LOG_PATH, "a");