Remove recordings feature, replay sessions directly, bump to 0.6.0

Recordings were just a thin named pointer over an already-captured
session's events, so the whole separate feature (recordings table, API
routes, pages, UI) is gone: any completed session can now be named and
replayed directly. Replaying no longer creates a session or duplicates
events of its own - it just bumps the source session's playCount/lastPlayedAt.

Also renames play_sessions/playSession(s) to sessions/session(s) throughout
the schema, queries, API routes, and UI for consistency, and updates the
README to match the new flow.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

drizzle/meta/_journal.json

@@ -8,6 +8,27 @@
       "when": 1787617808883,
       "tag": "0000_bouncy_anita_blake",
       "breakpoints": true
+    },
+    {
+      "idx": 1,
+      "version": "6",
+      "when": 1787856296915,
+      "tag": "0001_drop_recordings",
+      "breakpoints": true
+    },
+    {
+      "idx": 2,
+      "version": "6",
+      "when": 1787856317550,
+      "tag": "0002_add_session_replay_fields",
+      "breakpoints": true
+    },
+    {
+      "idx": 3,
+      "version": "6",
+      "when": 1787950004000,
+      "tag": "0003_rename_sessions",
+      "breakpoints": true
     }
   ]
 }