feat: implement shared-album multi-user photo album

Backend (Go/Gin/pgx): env config, pgx pool with retries, Garage S3 client
(path-style, region garage), embedded golang-migrate migrations, JWT auth with
refresh rotation, albums CRUD, members/roles/invites with no-escalation matrix,
photo upload + async imaging/goexif WebP variants, cursor pagination, presigned
URLs, likes/comments, SSE hub (album + personal), notifications, share links.

Frontend (SvelteKit 2 + Svelte 5 + Tailwind v4): API wrapper with 401 refresh,
auth store, all screens, Uploader/PhotoGrid/Lightbox/Comments, SSE client with
reconnect + REST catch-up, three themes + system via data-theme.

Deploy without Docker: Makefile builds the frontend into backend/static and
embeds it (go:embed) into a single statically linked binary; systemd unit and
nginx SSE example included.

Use gen2brain/webp (-tags nodynamic) instead of cgo kolesa-team/go-webp to keep
CGO_ENABLED=0 static builds; design.md/proposal.md updated accordingly.

backend/internal/sharelinks/handlers.go

@@ -0,0 +1,58 @@
+package sharelinks
+
+import (
+	"net/http"
+	"time"
+
+	"github.com/gin-gonic/gin"
+
+	"shared-album/internal/auth"
+	"shared-album/internal/httpx"
+)
+
+type Handler struct {
+	svc *Service
+}
+
+func NewHandler(svc *Service) *Handler { return &Handler{svc: svc} }
+
+type createRequest struct {
+	ExpiresIn string `json:"expires_in"`
+}
+
+func (h *Handler) Create(c *gin.Context) {
+	var req createRequest
+	_ = c.ShouldBindJSON(&req)
+	var ttl time.Duration
+	if req.ExpiresIn != "" {
+		d, err := time.ParseDuration(req.ExpiresIn)
+		if err != nil {
+			httpx.RespondError(c, httpx.BadRequest("invalid_expires_in", "invalid expires_in duration"))
+			return
+		}
+		ttl = d
+	}
+	link, err := h.svc.Create(c.Request.Context(), c.Param("id"), auth.UserID(c), ttl)
+	if err != nil {
+		httpx.RespondError(c, err)
+		return
+	}
+	c.JSON(http.StatusCreated, gin.H{"share_link": link})
+}
+
+func (h *Handler) List(c *gin.Context) {
+	list, err := h.svc.List(c.Request.Context(), c.Param("id"), auth.UserID(c))
+	if err != nil {
+		httpx.RespondError(c, err)
+		return
+	}
+	c.JSON(http.StatusOK, gin.H{"share_links": list})
+}
+
+func (h *Handler) Revoke(c *gin.Context) {
+	if err := h.svc.Revoke(c.Request.Context(), c.Param("id"), c.Param("link_id"), auth.UserID(c)); err != nil {
+		httpx.RespondError(c, err)
+		return
+	}
+	c.Status(http.StatusNoContent)
+}