myCarConnect sync API (what the phone apps call today)
=====================================================

Changes since version 5
-----------------------
1. Trips get one new field, "times": when the car reached each point of "path", so a replay keeps
   the real pace (stops at signals included).
     - a string of whole seconds after the trip's startAt, comma-separated, one per point of
       "path", in the same order: "0,5,9,14,..."
     - "" (empty) for trips recorded before times were kept; keep it as it comes. A trip stored
       without the field (everything version 5 kept) may come back without it: the apps read a
       missing "times" the same as "" (no timings), so old trips need no change
     - about 5 characters a point, so up to about 100 KB for a long trip
   Store it with the trip and send it back exactly as received (version 5 drops it today).
Nothing else changes: same URLs, key, YouTube list, merge and removal rules.

One URL, two lists. The apps build it from stream.php's address:

    https://<your server>/.../api/history.php?key=<the stream.php key>
    https://<your server>/.../api/history.php?key=<the stream.php key>&list=trips

Every call is an HTTP POST with a JSON body (Content-Type: application/json) and must answer
200 with a JSON body. A wrong or missing key: 403. Anything else that goes wrong: any non-2xx
code with a JSON body {"error": "what went wrong"}; the app shows/logs that text and tries again
later, keeping its own copy meanwhile. (A plain GET with the key may return the YouTube list
the same way; the apps only use POST.)

Times are Unix milliseconds (UTC). Keep the files where the web server cannot hand them out.


1) YouTube list  (POST ...history.php?key=KEY)
------------------------------------------------
Request: the phone's whole list and its removals.

    {
      "items": [
        {"id": "mjO5zQD3pbU", "url": "https://www.youtube.com/watch?v=mjO5zQD3pbU",
         "title": "Zehni Azmaish Season 14 New Kalam", "at": 1791206250726}
      ],
      "removed": {"uji7l0WgXx4": 1791290000000}
    }

  id      YouTube video id, exactly 11 characters of A-Z a-z 0-9 _ -  (refuse anything else)
  url     always https://www.youtube.com/watch?v=<id>  (you may rebuild it from id)
  title   may be empty; keep a known title if a newer entry arrives without one
  at      when it was last played on that phone
  removed id -> when it was removed on a phone

Merge on the server, then answer with the full merged result in the same shape:
  - per id, the entry with the larger "at" wins;
  - removed: per id keep the larger time;
  - an entry is dropped when removed[id] >= entry.at (a removal beats older plays, a newer
    play brings it back);
  - order items newest "at" first; no limit on the number of items;
  - removals may be forgotten after 30 days.

Response:  {"items": [...merged, newest first...], "removed": {...}}
           (send "removed": {} not [] when empty)


2) Trips  (POST ...history.php?key=KEY&list=trips)
---------------------------------------------------
Request: only what changed on that phone since its last sync, plus all its removals.

    {
      "since": 1791285689375,
      "trips": [
        {"id": 1791200000000, "startAt": 1791200000000, "endAt": 1791200900000,
         "distanceM": 7350.5, "startName": "Road 12, Banjara Hills, Hyderabad",
         "endName": "Charminar, Hyderabad", "destination": "Charminar",
         "note": "", "tag": "work", "source": "", "updatedAt": 1791200950000,
         "path": "_p~iF~ps|U_ulLnnqC_mqNvxq`@", "times": "0,312,900"}
      ],
      "removed": {"1791100000000": 1791286000000}
    }

  id         number (the trip's start time; up to 16 digits) - the key of the trip
  path       the route as a Google encoded polyline (1e-5 degrees); can be long - allow
             at least 200 KB per trip and a few MB per request
  source     "unit" for a drive the head unit recorded itself, "" for a phone's
  times      seconds after startAt at which each point of path was reached, comma-separated,
             one per point ("" for older trips); store and return it unchanged
  updatedAt  when the trip was last created or edited on a phone
  since      the "now" value your last answer gave this phone (0 the first time)

Server rules:
  - for each incoming trip: store it unless removed[id] >= its updatedAt, or the stored copy
    has an updatedAt >= it; when stored, stamp it with the server's current time (serverAt);
  - for each removal: keep the larger time per id and delete that trip;
  - answer with every stored trip whose serverAt > since (changes from any phone), all
    removals, and "now" = the server time you used as the stamp.

Response:

    {"now": 1791285689446,
     "trips": [ {... same fields as above, serverAt may be included ...} ],
     "removed": {"1791100000000": 1791286000000}}

"Clear" on a phone sends every trip id in "removed", so removed trips never come back.
A drive both the Pixel and the unit recorded (overlapping times) is tidied up on the phones;
the server stores both.