Use SyntaxCore ConfigManager for PlotsX startup and reload

[WieszczY85]

PlotsX previously filled missing configuration fields manually and kept a stale Bukkit view after writing the file. Startup now uses SyntaxCore.init(this), assigns SyntaxCore.logger, and loads the main YAML through ConfigManager before plot/database services initialize. Successful loading refreshes Bukkit's config and pluginConfig; /ptx reload follows the same path while retaining the claim-mode restart guard.

The bundled schema advances to 103 with steps 100 → 101 → 102 → 103. Migration preserves raw user values, including unknown nested maps/lists, while adding missing defaults. Database selections and credentials are retained. Language completion remains separate and now uses strict parsing: malformed YAML cannot become an empty configuration which is then overwritten with defaults. Reload prevalidation also uses strict parsing. Runtime/compile coordinates use SyntaxCore 2.0.0-R0.1-SNAPSHOT; teardown explicitly closes core.

Validation: full test/build passed, 217 tests with zero failures and zero skips. Twelve configuration tests include parameterized loops covering:

• Every customized leaf of the actual bundled template, plus false/zero/empty strings/lists and unknown nested settings.
• Missing nested default fields without overwriting custom values.
• Historical/unversioned schemas, fresh installation, unchanged current/future schemas, stable repeated load, and Bukkit readback.
• Exact backup present before callbacks; failed migration preserves original bytes; retries preserve each old backup; existing backup paths use unique siblings; denied backup writes prevent migration callbacks.
• Malformed YAML across unversioned/old/current/future schemas with no default replacement or staging residue.
• Language completion preserving user values, malformed language/reload YAML, invalid templates and incompatible sections leaving original bytes unchanged.

Consumer tests invoke the resolved SyntaxCore file engine reflectively to exercise the actual loader without a live JavaPlugin or new mocking dependency. Verified packaged schema 103 and runtime core coordinates. Live server smoke tests were not run.

Backup is once per migration attempt/chain, not per individual version step. Parsing precedes backup/mutation; parse failure leaves the original intact. Current/future schemas are read without rewriting, adding missing fields on disk, or creating migration backups. Documentation explains these boundaries and startup-only settings.