refactor: extract spline math, consolidate packet parsing, decompose TransportManager

Extract CatmullRomSpline (include/math/spline.hpp, src/math/spline.cpp) as a
standalone, immutable, thread-safe spline module with O(log n) binary segment
search and fused position+tangent evaluation — replacing the duplicated O(n)
evalTimedCatmullRom/orientationFromTangent pair in TransportManager.

Consolidate 7 copies of spline packet parsing into shared functions in
game/spline_packet.{hpp,cpp}: parseMonsterMoveSplineBody (WotLK/TBC),
parseMonsterMoveSplineBodyVanilla, parseClassicMoveUpdateSpline,
parseWotlkMoveUpdateSpline, and decodePackedDelta. Named SplineFlag constants
replace magic hex literals throughout.

Extract TransportPathRepository (game/transport_path_repository.{hpp,cpp}) from
TransportManager — owns path data, DBC loading, and path inference. Paths stored
as PathEntry wrapping CatmullRomSpline + metadata (zOnly, fromDBC, worldCoords).
TransportManager reduced from ~1200 to ~500 lines, focused on transport lifecycle
and server sync.

Signed-off-by: Pavel Okhlopkov <pavel.okhlopkov@flant.com>

include/game/transport_path_repository.hpp

@@ -0,0 +1,67 @@
+// include/game/transport_path_repository.hpp
+// Owns and manages transport path data — DBC, taxi, and custom paths.
+// Uses CatmullRomSpline for spline evaluation (replaces duplicated evalTimedCatmullRom).
+// Separated from TransportManager for SOLID-S (single responsibility).
+#pragma once
+
+#include "math/spline.hpp"
+#include <cstdint>
+#include <vector>
+#include <unordered_map>
+#include <glm/glm.hpp>
+
+namespace wowee::pipeline {
+    class AssetManager;
+}
+
+namespace wowee::game {
+
+/// Metadata + CatmullRomSpline for a transport path.
+struct PathEntry {
+    math::CatmullRomSpline spline;
+    uint32_t pathId = 0;
+    bool zOnly = false;       // Elevator/bobbing — no meaningful XY travel
+    bool fromDBC = false;     // Loaded from TransportAnimation.dbc
+    bool worldCoords = false; // TaxiPathNode absolute world positions (not local offsets)
+
+    PathEntry(math::CatmullRomSpline s, uint32_t id, bool zo, bool dbc, bool wc)
+        : spline(std::move(s)), pathId(id), zOnly(zo), fromDBC(dbc), worldCoords(wc) {}
+};
+
+/// Owns and manages transport path data.
+class TransportPathRepository {
+public:
+    TransportPathRepository() = default;
+
+    // ── DBC loading ─────────────────────────────────────────
+    bool loadTransportAnimationDBC(pipeline::AssetManager* assetMgr);
+    bool loadTaxiPathNodeDBC(pipeline::AssetManager* assetMgr);
+
+    // ── Path construction ───────────────────────────────────
+    void loadPathFromNodes(uint32_t pathId, const std::vector<glm::vec3>& waypoints,
+                           bool looping = true, float speed = 18.0f);
+
+    // ── Lookup ──────────────────────────────────────────────
+    const PathEntry* findPath(uint32_t pathId) const;
+    const PathEntry* findTaxiPath(uint32_t taxiPathId) const;
+    bool hasPathForEntry(uint32_t entry) const;
+    bool hasTaxiPath(uint32_t taxiPathId) const;
+
+    // ── Query ───────────────────────────────────────────────
+    bool hasUsableMovingPathForEntry(uint32_t entry, float minXYRange = 1.0f) const;
+    uint32_t inferDbcPathForSpawn(const glm::vec3& spawnWorldPos, float maxDistance,
+                                  bool allowZOnly) const;
+    uint32_t inferMovingPathForSpawn(const glm::vec3& spawnWorldPos,
+                                     float maxDistance = 1200.0f) const;
+    uint32_t pickFallbackMovingPath(uint32_t entry, uint32_t displayId) const;
+
+    // ── Mutation ─────────────────────────────────────────────
+    /// Store or overwrite a path entry (used by assignTaxiPathToTransport).
+    void storePath(uint32_t pathId, PathEntry entry);
+
+private:
+    std::unordered_map<uint32_t, PathEntry> paths_;
+    std::unordered_map<uint32_t, PathEntry> taxiPaths_;
+};
+
+} // namespace wowee::game